Of all the Firefox add-ons I have installed the one I’ve come to rely on is the official Delicious Bookmarks add-on.
This and many other add-ons have been incompatible with Firefox since the release of Firefox 4 back in March. One of the work-a-rounds was to disable add-on compatibility checking in Firefox.
To get incompatible add-ons working in Firefox 4 I’d followed the instructions here replacing the preference name extensions.checkCompatibility.3.6 with extensions.checkCompatibility.4.0
Unfortunately, with the release of Firefox 5 this week, just 3 months after the release of Firefox 4, many add-ons are once again not working. It’s easy enough to fix though. Just follow the instructions in the link above this time replacing the preference name extensions.checkCompatibility.3.6 with extensions.checkCompatibility.5.0