580205 - lockPref in "mozilla.cfg" doesn't seem to work properly with Private Browsing

Status: UNCONFIRMED

(Firefox :: Settings UI, defect)

Description

[Ralf Ritter]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.1; de; rv:1.9.1.10) Gecko/20100504 Firefox/3.5.10
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; de; rv:1.9.1.10) Gecko/20100504 Firefox/3.5.10

I'm using a "mozilla.cfg" to lock serveral Preferencies. For example:
lockPref("browser.formfill.enable", false);
When I open then Preferencies Menu, the Option is set correcly to "false", but it is not grayed out. When I click the Option, it get's grayed out. 
I then switched the Option to Start Firefox in Private Browsing Mode two times and the above Option "browser.formfill.enable" was no longer grayed out. 
Works as designed?

Reproducible: Always

Steps to Reproduce:
1. Start Firefox in "normal" mode
2. Open Menu "Perferencies"
3. Check Option "browser.formfill.enable" as set by "mozilla.cfg" - Option is  not grayed out.
4. Switch this Option once - Option is  grayed out.
5. Switch Option "Start Firefox automaticly in private mode" (don't know the correct expression, I have a german version) twice - the Option "browser.formfill.enable" is editable.



Expected Results:  
1. Option "browser.formfill.enable" is not editable when opening the Preferencies Menu.
2. Switching the Option "Start Firefox automaticly in private mode" does not make "the other" Option editable.

I noticed this behaviour for other preferencies too.