According to this Discogs page, the API used for querying the site in MP3 Diags stable up to 1.0.9 and MP3 Diags Unstable up to 1.1.08 will be turned off on January 15th. So I changed the code to use the new API. The unstable branch got the change in 1.1.09. Since it worked OK for me and I didn't receive any complaints from anybody else, I assumed it was OK and I backported the change to the stable branch, in version 1.0.10.
So anybody who wants to use the Discogs integration after January 15th 2012 should have one of these versions (or something newer, as I release them): 1.1.09 unstable or 1.0.10.