Simultaneous-Use for roaming wireless user

Hi all, We enabled Simultaneous-Use checking with checking against accouting data stored in MySQL database. However, found that some of the Stop records are not received and this makes Simultaneous-Use checking fail. Seems roaming users will always encountered this problem. I wonder if I've to use checkrad instead but seems our AP (Aurba) is not permitted as nastype in clients.conf. Would anyone please advise any solution for this issue? Thank you very much. Best Regards, /ST Wong