I just upgraded to WP 2.0.6 about four days ago. Before and after the upgrade, I was running the latest Akismet plugin, 1.2.1. I deactivated Akismet before the upgrade and reactivated after, as usual.
Since the upgrade, Akismet has let through almost every single spam comment I've gotten (upwards of a thousand), maybe 100%. It doesn't seem to be learning from the huge number of comments I moderated as spam, either.
Anyone have any idea what might be going wrong? I double-checked that the API key was entered, and it was. I'm lost as to why the plugin isn't working.