When disabling an add-on (plugin or extension) via the context menu, (right-click it and select "Disable"), then right-clicking again, you can find that it still says 'Disable' in the context menu. Clicking 'Disable' again does nothing. Solution: Show 'Enable' menu item in context menu for already disabled extensions and plugins.
It looks like the context menu only changes when you select another panel and go back to the original one. Then you can see the correct item. This affects 'Enable' as well (depending on the state)
It changes if you select a different add-on in the list too. Need to update the commands after any add-on changes state.
Created attachment 502607 [details] [diff] [review] Patch v1
Landed: https://hg.mozilla.org/mozilla-central/rev/6e04a051a8da Automated tests cover this well.
Verified fixed with Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:2.0b10pre) Gecko/20110112 Firefox/4.0b10pre ID:20110112033217