Why am I unable to logon selected user?

I have created 2 users in Windows XP(Home edition), and recetly, having problems looging into windows with one of the user(A).When I try to log on to the (A), it will start to load personal options and then it will sort of hang in the explorer. Mostof the time can log off using task manager but smtimes have to force shut down. Sometimes, there don;t seem to have a problems starting up. This ONLY applies to user (A). I have scanned the disk and did a virus check but all was clear.I am currentlyusing Norton Antivirus and it is up to date and have also updated Windows. Why is there such a problem?