Win 7 64bit Portserver TS 8 modem problem


I have a problem with running our Portserver TS 8 with modems on Win 7 64bit.
There are some devolo microcoms 56k-i and the system works fine under Win XP for a while so I asume there is no HW problem.
Problems comes with win7 64bit, I am able to install portserver and modems are automatically detected, installed succesfully and that is all.
Usual behavior is that modems does not response at all, but some times I able to get info from modem via device manager. It never called.
Possibly problem coud be that there is valid modem driver for Win7 64bit, so I have to use windows generic (but modem works fine when connected directly to same PC)
Any advice what should I try to make it work?

Thank you very much