seemingly random crashes, 100% cpu

hello,

i'm having a weird problem at the moment - when i'm connected, as if by
random, i get huge lockups preceded by 100% cpu usage, used by
khsfd/modem. the keyboard doesn't respond at all for a while, and after
this lockup goes away (after about a minute or so) and the modem has
disconnected it still says it is busy, and i have to reboot to reconnect.

i'm using gentoo, with kernel 2.6.20.7 and driver
version 7.60.00.02, full version. i am using a conexant hsf pci modem. i
have made a point of building kernels with and without the pre-empt
options, and fiddling with tcp/ip and netfilter options, but it doesn't
seem to make any difference. i'm on an smp system.

thanks in advance.