Hangs up and other problem

[Vozhd]

Hello. I have the following hardware:
ASUS A7N266-E (nForce)
Athlon XP 1400+
RAM 654 MB
Modem Zyxel OMNI 56k UNO (USB)

There are following problems:
1. On kernel 2.4.22 (20,23) + alsa 0.9.8 when I launch mplayer or any game with sound, in some minutes system hangs up. When I turn off sound, for example, mplayer -nosound, all is working fine. I tried to use nforce-audio instead of alsa but the result is the same. Modem works fine.
2. On kernel 2.6.0-beta11 sound works wonderfull, but when modems is connecting every 2-5 seconds whole system freeze for 5-10 seconds.

There are no any errors in dmesg. How can i solve this problems?