With the recent release of Firefox 3.0.1, some users are finding that their add-ons that had been working prior suddenly stopped working due to incompatibility. This is an actually a problem that is being caused by the add-on developers. While they have specified their compatibility range as Firefox 2.0-3.0.*, the have incorrectly declared the add-ons’ maxVersion as “3.0” (works up to Firefox 3.0 only) instead of “3.0.*” (works with any Firefox 3.0 build).
While most of the add-ons hosted via AMO are correctly configured, this may not be the case for add-ons hosted else where. Should you run into a case where an add-on has been disabled in Firefox 3.0.1 due to being incompatible, you will need to contact the add-on developer so they can correct their error.
News Source: Basil’s Bodacious Blog