Running WP 3.1 and NoSpamNX 4.0.2 -- installed OpenID and it totally broke the wp-admin interface with an error message displayed about NoSpamNX malfunctioning. Now maybe this is the fault of NoSpamNX. I dunno. But up until I downloaded and installed OpenID, WP and NoSpamNX were functioning just fine...
Anyway, had to connect to my DB and manually disable all the plugins and re-enable them one by one. I left OpenID disabled. Fortunately, the site itself stayed up through this process, so it wasn't all bad.