modem conflict?

I have a duron 1300 with a ga-7zxe motherboard with 256mb ram running win98. I recently upgraded to ati 64mb apg card. But when I installed my modem and connect to the internet everything just takes a turn for the worse. First I get a couple differnt fatal execption errors, then after reboot it wants to preform scan disk and start in safemode. In device manager there are no conflicts and everything shows to be running ok. I have the most updated drivers for everything. This behavior only occursafter the moden is installed and connected for the first time, without the modem everything works ace. I look forward to your suggestions. Thanks.