Freezing online & immed after log off

I have this problem with 2 users. I have
increased the time out with my ISP and stopped the timeout on the browser. I have increased the memory in both to well over 64mg. I have dumped the temp files and history files and lowered the number of days for info to reside in history. There is gigs
of drive space open and I use 56k modems.

We do share a modem line (taking turns) but the users were not interrupted. The ISP has
checked the settings. How do U solve this?