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I am getting an error message when I open Firefox 5 (Win.Vista) "TypeError:Components.classes[cid] is undefined." How can I get rid of this? Thank you.

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  • 81 have this problem
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  • Last reply by rfeichel

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Only started since the upgrade. Windows Vista Home 32 bit. The error message reads: "TypeError:Components.classes[cid] is undefined."

Only started since the upgrade. Windows Vista Home 32 bit. The error message reads: "TypeError:Components.classes[cid] is undefined."

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This issue can be caused by an add-on that isn't working properly.

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

If it does work in Safe-mode then disable all 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 Safe mode start window to disable all extensions.
  • Close and restart Firefox after each change via "File > Exit" (Mac: "Firefox > Quit"; Linux: "File > Quit")

In Firefox 4 you can use one of these to start in Safe mode:

  • Help > Restart with Add-ons Disabled
  • Hold down the Shift key while double clicking the Firefox desktop shortcut (Windows)

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Try the suggested idea above. I just disabled all the add-ons which were not compatible with FF 5 and did a FF restart. That fixed the problem. I then enabled each one, one at a time, with a FF restart until the problem came back. I then disabled that add-on.