I‘ve seen this error quite a few times when trying to check for extension updates. Either it does not return anything and says “no updates found” or “an error occurred while looking for updates”. while there may be different reasons to why it is happening, here’s a small tip to help you peek in and take a look.

1. Go to about:config
2. Set the preference extensions.logging.enabled to true
3. restart firefox
4. Open the Error Console window
5. Check for updates.
6. looking in the error console

What this does is it logs all the errors and messages about extensions to the error console window. And you may find the message that you are looking for. May be the update.rdf is not there on the server or is not a valid rdf or xml. It could also be that the signature check is failing; this is happening mostly on Firefox v3 onwards because the addon security model was updates to secure users from man-in-the-middle attacks. Hope this helps.

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