play.google.com and Google Play app out of sync Having become fed up with a custom ROM i was using, I reverted back to a previous ROM via a nandroid backup (through CWM Touch).
It would appear that the backup preserved all my installed apps and data (Was under the impression they didn't, so this surprised me somewhat), but since then the 'My Apps' listing on the google play website has been out of sync with what is actually on my phone. I also seem unable to request (un)installation through the web interface.

Help would be muchly appreciated.
It may be the link to the Play store was lost. I think if you install an app from, say, the amazon app store, Google Play will not be able to update or uninstall it, as the link is gone. Similarly, restoring an app from a previous rom backup may not create that link.

Titanium Backup can recreate the links (the free version can can't do this). Or you could uninstall the app and try installing it fresh from Google Play.