RAS freezes

Hi,
I have some problems with RAS, it freezes approximately once a week. Once
it is froze, I cannot see the outgoing and incoming connections on the server
because those windows are froze too. And I need to reboot the server to be
up and running again.

Here is a brief overview of the system. The system is used for monitoring
and controlling some remote devices, approximately 200 now. The devices can
connect to the server and the server can also initiates a connection with the
devices. I have 13 lines on the server, 3 for incoming calls and 10 for
outgoing calls, and they are well split, the incoming and outgoing calls
always use different lines. A connection is maintained for 1 to 30 minutes,
and approximately 3000 connections are established per day. Everything is
running well for approximately one week.

Each time I close a connection I call ras.hangup function and I wait that
the handle become invalid (then not used anymore) before reusing it. I also
noticed that the ras.hangup call never comes back once RAS service is froze.

Thanks for your help.