I had the same problems alot. I finally stopped using ADDIP and I just write down the IP, go to a reverse IP lookup and ban the netblock range for the violator. This seems cleaner and prevents the hated DHCP users from jumping right back in.
in my server.cfg i have
seta g_filterban 1
Then in the banlist.cfg I have the g_banips cvar with the IP ranges for all the naughty players. I have noted that if I add an IP and also have his IP range banned then it apparently un-bans the whole block.