Firefox catches a cold

Yesterday I upgraded to Firefox 1.5.0.1. Everything seemed fine. This morning though I can’t open any window without getting this error message:

XML Parsing Error: no element found
Location: chrome://browser/content/browser.xul
Line Number 1, Column 1:


Surprisingly even reinstalling Firefox doesn’t help. Neither does rebooting the machine. However logging in as a different user does fix the problem and allow me to run Firefox, but when I log back in as my usual self I get this error message again. That suggests it’s a preferences problem. I hid the Library/Mozilla folder but that didn’t fix anything. Let’s try hiding Library/Preferences/org.mozilla.firefox.plist. Nope, that doesn’t fix anything either.

Ah, wait a minute. The Firefox preferences aren’t the same place the Mozilla prefs are. They’re in Library/Application Support/Firefox instead of Library/Mozilla. Let’s try getting rid of that. Ok. That seems to have something to do with it. Now Firefox will start. Surprisingly after the moving the old Profile back, everything works again. I can’t explain it; but the solution to this problem seems to be:

  1. Quit Firefox
  2. Rename Library/Application Support/Firefox to Library/Application Support/Firefox2
  3. Launch Firefox
  4. Quit Firefox
  5. Move Library/Application Support/Firefox to the trash
  6. Rename Library/Application Support/Firefox2 to Library/Application Support/Firefox
  7. Launch Firefox

Oops. That fix appears to be only temporary. Now it’s doing it again. OK. Let’s think about the error message for a minute. What is it telling me? It appears to say that in the file browser/content/browser.xul there’s no root element. (Side note: I can probably figure this out, but there’s no excuse for showing this message to an end user. You shouldn’t need to have written a dozen books about XML just to use a web browser.) Where might that be? I don’t see any such file, but I do see that the Profile contains a chrome folder. This contains an overlayinfo folder, which contains browser folder, which contains a content folder. However this does not contain a browser.xul file. Maybe it’s missing? Once again, let’s try renaming the Firefox folder, so it will create a new profile.

Hmm, that did not create the missing file; but it didn’t create overlayinfo/browser/content either? Maybe I can just delete that folder. Let’s hide it and see what happens. Nothing. Same problem as before.

Oh wait. Looks like there are more chrome directories in the extensions folder. Let’s try hiding them. OK, that seems to have worked. Will it stick? Yes, I can quit and relaunch Firefox. And adding them back reproduces the problem. So I’m reasonably confident I’ve isolated the problem to the extensions.

The next obvious question is which extension caused the problem. I have quite a few: Web Developer, AdBlock, XForms, Sage, Tab Downloader, GreaseMonkey, and Customize Google. I could try adding them back one by one, but I don’t really have the energy for that right now. I will keep an eye on this in the future.

Anyone have any idea what’s going on here? This bug might be relevant, but then again might not be. I’ve filed my own bug addressing the user interface issues, leaving aside the root cause of the problem.

10 Responses to “Firefox catches a cold”

  1. Dan Says:

    It just happened to me, all i did was start it in safe mode once, close it and open it again in normal mode and it started working.

  2. grafwritah Says:

    Same deal with me on Firefox 2.0. Started up in safe mode, disabled all extensions, started up regularly no problem, enabled extensions a few at a time until all were added back and Firefox started back up ok.

  3. pete Says:

    ya, this happened to me today as well

  4. pete Says:

    Same error for me when I safe mode start it.

  5. pete Says:

    Hey this worked for me-
    http://kb.mozillazine.org/Safe_Mode

    run > firefox -safe-mode
    disable all extentions

    restart firefox and all is well

  6. k3nn37h Says:

    It comes kinda late, but I’ve found out it’s Grease Monkey causing the problem.

  7. pommerdog Says:

    i disabled “PanelApp” and the problem went away for me. Not sure that it’s so app-specific… i only had 3-4 add-ons installed, this one i didn’t remember, so got rid of it…. and problem left too. greasemonkey caused k3nn37h the problem, so maybe just try disabling addons one at a time will help track it down for some people..

  8. Bastion Says:

    Same problem here:
    http://groups.google.com/group/mozilla.feedback.firefox/browse_thread/thread/191e9a8221ded96c

  9. Peta Michaela Gergen Says:

    Hi

    I had the same problem after installing Adblock Plus (AP).
    Could also only get 1 window (may tabs) but not more than one window open.

    Uninstalled AP and restated FireFox and the problem is gone.
    The Chrome XML messages are gone and I can open multiple windows again.

    I suspect that is is a configuration item in Adblock that is the problem.

    Best regards
    Peta M Gergen

  10. Peta Michaela Gergen Says:

    Hi

    I had the same problem after installing Adblock Plus (AP).
    Could also only get 1 window (may tabs) but not more than one window open.

    Uninstalled AP and restated FireFox and the problem is gone.
    The Chrome XML messages are gone and I can open multiple windows again.

    I suspect that it is a configuration item in Adblock that is the problem.

    Best regards
    Peta M Gergen

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