I recently unticked the "pre-released updates" option in Software Sources on my Ubuntu Lucid 10.04.1 installation. The Ubuntu wiki states the following regarding this source:
The proposed updates are updates which are waiting to be moved into the recommended updates queue after some testing. They may never reach recommended or they may be replaced with a more recent update.
Roughly 20 installed packages have indeed not made it into recommended updates, and occasionally cause conflicts when I install new software, as related packages of the newer version are unavailable now that I've disabled the source.
How can I force a downgrade of all packages for which an earlier version exists in a enabled repository?