Thank you for the link to your crash report.

The crash signature is associated with a bug related to the Zimbra email server. Does that connect at all with your setup, or does that sound unrelated?

Could you disable your avast! Online Security extension? It has been linked to a number of strange issues in other threads and we should try to rule that out. Open the Add-ons page using either:

• Ctrl+Shift+a
• orange Firefox button (or Tools menu) > Add-ons

In the left column, click Extensions. Here you can disable the extension. If a link appears above it to restart Firefox, go ahead and do that.

Firefox will attempt to restore your open tabs, and you can confirm that it has been successfully disabled. If it stays enabled, please check your user.js file to see whether it is interfering with your ability to changes settings. This article describes how to access that file: How to fix preferences that won't save.

If you see file names like prefs, sessionstore, and user without the .js extension, you may want to turn on viewing of file extension so that you can work with your settings folder more accurately. This article has the steps for that: http://support.microsoft.com/kb/865219.

Avast is also mentioned in the linked bug report, so give disabling avast! Online Security a try.

• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes
• bug 856796 - crash in JSC::Yarr::Interpreter when selecting 'stop script'