Well, I clicked "IP:logged" [...] put it in the "last IP" space
Okay, problem number one - it's possible for a user's IP to change mid-session. In such a case, this change wouldn't be recorded in his or her profile. There is no mechanism to search posts for IPs at this time.
As for the other problems... first things first, run a member metadata rebuild, as that will help. Second, as this data is stored in the member file, only members that have been active since you upgraded will have any last login/last session IP info. This may result in unusual results on some queries.