pptp tunnel strange problems

I have a Mikrotik router, version 2.8 that I am using as my main router at our small office. We have one client that also has a mikrotik router and we have a pptp tunnel between the routers.

Everything seems to work well, until I try to transfer a large file from their network, or anything that would require lots of bandwidth.

The connection is working, and I get the first chunk of the data I requested, and then all of the sudden everything just stops responding. It does not transfer any more data or time out.

The strange part is, that this seems to only be happening with the Mikrotik VPN tunnels. If I disconnect the tunnel, and use Windows PPTP to connect to the remote Mikrotik, everthing works great.

Has anyone seen this problem before, or have any idea where I could start looking for the solution?

there were all kinds of tunnel problems with early 2.8 firmware. i would recommend updating to 2.8.19 (or later).

regards.
matthias