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Error "TypeError: Components.classes[cid] is undefined" when opening Firefox - every time it is opened!!

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Since installing Firefox 4 I receive this error message "TypeError: Components.classes[cid] is undefined" each time Firefox is opened and when trying to access some websites. Very aggravating!!

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That indicates that you are using an add-on that is not compatible with Firefox 4. For details of how to troubleshoot this to find out what one is causing the problem see https://support.mozilla.com/kb/Troubleshooting+extensions+and+themes

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Chosen Solution

That indicates that you are using an add-on that is not compatible with Firefox 4. For details of how to troubleshoot this to find out what one is causing the problem see https://support.mozilla.com/kb/Troubleshooting+extensions+and+themes

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After I disabled the last add-on that was installed prior to upgrading to version 4 the error was eliminated. Thanks!!