Well, the original forum for this bug is now locked, so I couldn't post to it. Please excuse my starting a new topic.
Anyway, the same unpure client bug happened to me today during TRAIN, when I was playing with several other folks. First, I was kind of dead/alive. I couldn't move but I could see everyone running by me. I logged out and then twice got the "unpure client" message before successfully logging back in through Monster Browser.
Just thought I'd let you know the bug is still alive.