cable modem problems

I had a recent post of problems with a network card. Switching the card fixed that problem however I am still having issues and would appreciate any input. Here's an overview of the problem:
I originally was experiencing problems with my browser (ie6) after a short time period, of failing to bring up pictures and quite often not being able to find web page. Cable company recommended switching to network card because they are much more stable then usb connection. So I installed card and am still experiencing problems. After approx 20 mins, the "x's" start appearing where pictures are suppose to be if the page even appears. What I have found out is that if I run winipcfg and then release all, then renew all everything works again. After doing this, seems to be stable for quite awhile though still need to release/renew every so often. I am running win 98se, motorola cable modem. I have installed all patches, ran spyware remover, and virus scan. I plan on contacting cable company again, but think that I will get the runaround again. Any suggestions?