Ask your VPN service provider. You haven't provided any helpful information here.
come on! this is Macrumors. There Is No One that can help me in this situation?
Like brand has said, give us more information. Relevant log entries in the system log perhaps. You using a third party client?
its all i've done to do this:
Making a PPTP Connection.
Testing with encryption and without that( for different servers ).
and another ordinary settings.
i've test that in different situations and all i've got was the same.
its still connect, but accurately in 10 minutes sending and recieving will stop.
There is nothing in the system log when it disconnects?