Bugzilla

I did try to bisect it by manually downloading and installing previous versions of Nightly as in comment #8. 

_mozregression does not run on my Win7 OS and that has been the case for many years. There are Python errors. Installing various versions of Python didn't help either._

Looking at _Developer Tools ➜ Style Editor_, it may !!? relate to CSS `@import` as I don't see the files loaded. I also use `@import` in the browserAction pop-ups. Although, the pop-ups that don't have `@import` also fail.

As mentioned in the first post, commenting out the `<link rel="stylesheet" href="popup.css">` will result in the pop-up showing (but looking bad). This point does not relate to the issues in bug 1735347.

Please note that there are specific setting in `about:config` that relate to Win7. There are a few OS-specific locked entries as I found out when discussing anther matter in #amo:mozilla.org which may explain why the issue in not happening for everyone.

N.B. As I type and as pop-ups fail and as extension option pages fail, I opened a new Private window and everything works fine in that private window.
After a while, that private window will also start to experience the same failures and I would be forced to restart Firefox in order to access pop-up & options.

I did try to bisect it by manually downloading and installing previous versions of Nightly as in comment #8. 

_mozregression does not run on my Win7 OS and that has been the case for many years. There are Python errors. Installing various versions of Python didn't help either._

Looking at _Developer Tools ➜ Style Editor_, it may !!? relate to CSS `@import` as I don't see the files loaded. I also use `@import` in the browserAction pop-ups. Although, the pop-ups that don't have `@import` also fail.

As mentioned in the first post, commenting out the `<link rel="stylesheet" href="popup.css">` will result in the pop-up showing (but looking bad). This point does not relate to the issues in bug 1735347.

Please note that there are specific setting in `about:config` that relate to Win7. There are a few OS-specific locked entries as I found out when discussing anther matter in #amo:mozilla.org which may explain why the issue in not happening for everyone.

N.B. As I type and as pop-ups fail and as extension option pages fail, I opened a new Private window and everything works fine in that private window.
After a while, that private window will also start to experience the same failures and I would be forced to restart Firefox in order to access pop-up & options.

_PS. All my extensions are under development and are loaded unpacked (in case that has a bearing on the issue)_

I did try to bisect it by manually downloading and installing previous versions of Nightly as in comment #8. 

_mozregression does not run on my Win7 OS and that has been the case for many years. There are Python errors. Installing various versions of Python didn't help either._

Looking at _Developer Tools ➜ Style Editor_, it may !!? relate to CSS `@import` as I don't see the files loaded. I also use `@import` in the browserAction pop-ups. Although, the pop-ups that don't have `@import` also fail.

As mentioned in the first post, commenting out the `<link rel="stylesheet" href="popup.css">` will result in the pop-up showing (but looking bad). This point does not relate to the issues in bug 1735347.

Please note that there are specific setting in `about:config` that relate to Win7. There are a few OS-specific locked entries as I found out when discussing anther matter in #amo:mozilla.org which may explain why the issue in not happening for everyone.

N.B. As I type and as pop-ups fail and as extension option pages fail, I opened a new Private window and everything works fine in that private window.
After a while, that private window will also start to experience the same failures and I would be forced to restart Firefox in order to access pop-up & options.

_PS. In case this has a bearing on the issue, all my extensions are under development and are loaded unpacked as it has been for many years._

I did try to bisect it by manually downloading and installing previous versions of Nightly as in comment #8. 

_mozregression does not run on my Win7 OS and that has been the case for many years. There are Python errors. Installing various versions of Python didn't help either._

Looking at _Developer Tools ➜ Style Editor_, it may !!? relate to CSS `@import` as I don't see the files loaded. I also use `@import` in the browserAction pop-ups. Although, the pop-ups that don't have `@import` also fail.

As mentioned in the first post, commenting out the `<link rel="stylesheet" href="popup.css">` will result in the pop-up showing (but looking bad). This point does not relate to the issues in bug 1735347.

Please note that there are specific setting in `about:config` that relate to Win7. There are a few OS-specific locked entries as I found out when discussing anther matter in #amo:mozilla.org which may explain why the issue in not happening for everyone.

N.B. As I type and as pop-ups fail and as extension option pages fail, I opened a new Private window and everything works fine in that private window.
After a while, that private window will also start to experience the same failures and I would be forced to restart Firefox in order to access pop-up & options.

_PS. In case this has a bearing on the issue, all my extensions are under development and are loaded unpacked as it has been for many years._

**Update:**
It has already been 10 days and it appears that the failures, when happen, only happen for the above mentioned unpacked add-ons. I have 2 other addons (uBlock Origin & uMatirx) and their pop-ups haven't failed yet. Considering that loading stylesheets seems to be a factor, could there have been some changes to the stylesheet loading process on Oct 9th-10th  that is affected the loading from unpacked & out of Firefox own file system location?

I did try to bisect it by manually downloading and installing previous versions of Nightly as in comment #8. 

_mozregression does not run on my Win7 OS and that has been the case for many years. There are Python errors. Installing various versions of Python didn't help either._

Looking at _Developer Tools ➜ Style Editor_, it may !!? relate to CSS `@import` as I don't see the files loaded. I also use `@import` in the browserAction pop-ups. Although, the pop-ups that don't have `@import` also fail.

As mentioned in the first post, commenting out the `<link rel="stylesheet" href="popup.css">` will result in the pop-up showing (but looking bad). This point does not relate to the issues in bug 1735347.

Please note that there are specific setting in `about:config` that relate to Win7. There are a few OS-specific locked entries as I found out when discussing anther matter in #amo:mozilla.org which may explain why the issue in not happening for everyone.

N.B. As I type and as pop-ups fail and as extension option pages fail, I opened a new Private window and everything works fine in that private window.
After a while, that private window will also start to experience the same failures and I would be forced to restart Firefox in order to access pop-up & options.

_PS. In case this has a bearing on the issue, all my extensions are under development and are loaded unpacked as it has been for many years._

**Update:**
It has already been 10 days and it appears that the failures, when happen, only happen for the above mentioned unpacked add-ons. I have 2 other addons (uBlock Origin & uMatirx) and their pop-ups haven't failed yet. Considering that loading stylesheets seems to be a factor, could there have been some changes to the stylesheet loading process on Oct 9th-10th  that is affecting the loading from unpacked & out of Firefox own filesystem location?