OPEN VPN

Hi, after I configured OVPN on Mikrotik, I can connecting successfully to it, but I still has a problem that in windows XP client the connection is terminated after about 1 minute(there is no problem with windows 7, just in xp). In the show status, it tells me that the connection have been restarting.
Note that it is the same configuration and user on Windows 7 and XP.
I need your help buddies.