So after playing around with many of the other anti spam plugins for Wordpress, I've come the logical full circle back to Akismet. The problem is, for whatever reason, it's refusing to work!
WPMU 2.7.1, latest Akismet, placed in mu-plugins/ with the API key hardcoded (and triple checked). When I go to my dashboard, or the dashboard for any of the blogs, it's just returning the Blog not found, er? error message. I know it works from my server, as I have two other standalone installations of WP2.8 running Akismet just fine. So... any suggestions for where to look to fix this?
I've searched these forums and wordpress.org itself, without much luck. Seems everybody on there either forgot to allow outgoing connections for Akismet, or it just randomly started working for them.
