User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:5.0) Gecko/20100101 Firefox/5.0 Build ID: 20110615151330 Steps to reproduce: tried to download a file or image Actual results: the browser hangs and then windows 7 become unresponsive. It gets bad enough that I cannot even ctr-alt-del and have to restart by turning it off the power. I'm getting disk corruption also, severe enough disk problems that I'm unable to boot windows 7 and need to boot from a different install and run chkdsk. One chkdsk took 45 minutes to complete as it had enough problems. I have not had such problems in the past when losing power. Things work fine in FF 4 and things work fine in FF 5, until I download a file or image. I don't know if the extensions are a problem as currently I am reluctant to turn off the extensions and download with FF 5 due to corruption problems. I realize this might not be optimal but is a serious issue such that I cannot use FF 5.
I do not see the problem when using explorer, only FF 5.
Does the issue still occur if you start Firefox in Safe Mode? https://support.mozilla.com/en-US/kb/Safe+Mode How about with a new, empty profile? https://support.mozilla.com/en-US/kb/Basic+Troubleshooting#w_8-make-a-new-profile
Firefox can not hang/freeze or crash the OS. A usermode application doesn't have the system privileges to do that but Firefox could trigger a bug in a driver or other software with kernelmode privileges (drivers, Firewall products, Antivirus software). Firefox calls the installed Antivirus software for a scan after the download. Is it possible that your AV software is causing this ? Please open about:config, confirm the warning, enter "scan" in the top filter bar and change "browser.download.manager.scanWhenDone" to false.
Not sure why, but it went away as suddenly as it showed up.