HSP56 MicroModem + NT

I have HSP56 MicroModem on WinNT 4.0 + SP5.
I connect to the Internet via this modem using RAS. Everything is allrigth untill I try to disconnect. Blue screen of death appearing with stop code 0xA. It appears mostly times I do.
What`s wrong ? I think it`s probably driver problem.
Thank you.