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Error when starting Firefox 3.6. "Javascript Application error. Invalid username/password combination. If you continue to get this error, try entering your email address as your username." Any suggestions on what to look for to resolve this?

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When starting Mozilla Firefox 3.6, I get an error window which opens up additionally overtop my browser windows stating:

"Javascript Application"

followed with :

"Invalid username/password combination. If you continue to get this error, try entering your email address as your username."

Obviously it is happening with one of my email addresses/usernames & password combinations of which I know the username for (which I choose not to post here) and I'm not sure where to begin looking for a resolution to this problem.

Chosen solution

Yes, use Firefox's Troubleshoot Firefox issues using Safe Mode.


Start Firefox in Troubleshoot Firefox issues using Safe Mode to check if one of your add-ons is causing your problem (switch to the DEFAULT theme: Tools > Add-ons > Themes).

  • Don't make any changes on the Safe mode start window.

See Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems and Troubleshoot issues with plugins like Flash or Java to fix common Firefox problems

If it does work in Safe-mode then disable all your extensions and then try to find which is causing it by enabling one at a time until the problem reappears.

  • Use "Disable all add-ons" on the Troubleshoot Firefox issues using Safe Mode start window to disable all extensions.
  • Close and restart Firefox after each change via "File > Exit" (Mac: "Firefox > Quit"; Linux: "File > Quit")
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All Replies (4)

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Start Firefox in Troubleshoot Firefox issues using Safe Mode to check if one of your add-ons is causing your problem (switch to the DEFAULT theme: Tools > Add-ons > Themes).

  • Don't make any changes on the Safe mode start window.

See Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems and Troubleshoot issues with plugins like Flash or Java to fix common Firefox problems

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So what you're saying is I should start Firefox itself in Safe Mode, and not the computer itself?

Pls advise. Thanks!

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Chosen Solution

Yes, use Firefox's Troubleshoot Firefox issues using Safe Mode.


Start Firefox in Troubleshoot Firefox issues using Safe Mode to check if one of your add-ons is causing your problem (switch to the DEFAULT theme: Tools > Add-ons > Themes).

  • Don't make any changes on the Safe mode start window.

See Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems and Troubleshoot issues with plugins like Flash or Java to fix common Firefox problems

If it does work in Safe-mode then disable all your extensions and then try to find which is causing it by enabling one at a time until the problem reappears.

  • Use "Disable all add-ons" on the Troubleshoot Firefox issues using Safe Mode start window to disable all extensions.
  • Close and restart Firefox after each change via "File > Exit" (Mac: "Firefox > Quit"; Linux: "File > Quit")
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I was able to resolve this by disabling (under Tools - Add-ons) Yahoo! Mail Notifier

Hope this helps some of you also!