please help with instability issue

Hi,

Ive been trying to create a stable and good performance vpn server for some time now. With normal poptop i couldnt get good enough performance, so i tried accel-pptp. I know its not that mailing list, but maybe you can help, there are too few people on the other and they dont seem to have this issue.  

So my issue is:

Most of the time the server works like charm, without any problem, the speed is wonderful, but sometimes the connection just stops working.

Cannot ping server, no communication on link, but the connection stays online. Sometimes this behaviour occures after many hours, but sometimes immediatly after the connection.

And usually reconnecting does not fix it, because after a few seconds it goes bad again. Not sure what fixes, but if i let it rest for a while, it works again.

In the debug it seems as if nothing changed, when it stopps working (or at least i didnt notice anything)

As for the client, I’v observed the same symptoms on windows 7, vista, xp and various routers (draytek vigor, dd-wrt, asus sl200)

The server is up-to-date Fedora 11, 2.6.30.8-64.fc11.x86_64 kernel, pppd version 2.4.4.

Any idea where should i look for solution?  

Thanks,

András Kosztyu