they arnt msn...i had to go back to ichat and unblock them from there...i found that there names were under the block list (in ichat) multiple times. Like for some reason, i was pushing block instead of unblock many times.
I'm having the exact same problem using .81 and AIM. When I went to unblock the person, it wouldn't go through. I went to check and it still says "unblock" as the option. I had to go through AIM to actually unblock the person.
This is a known issue that affects some people, and there's a bug report tracking it. No ETA on a fix, but hopefully in the fairly near future. The workaround is to unblock using the official client (which is a pretty nasty workaround, so fixing this is a fairly high priority).