User is locked out of computer when logging on remotely

Hi, I have a remote user on windows 7 who comes in to the office approx. once per couple of weeks. When she is on site, she can log on to the 2003 domain with no problems. however, when she is away, the first few remote logons work with cached credentials. After a few days though, her account locks out and it can’t be used until she comes back into the office.

I’ve seen various discussions about cached credentials count but this seems to be related to the number of different users who can log on using cached credentials and not the number of logons for a single user.

Has anyone else come across this issue?