"Party poker has detected an error" message while multi-tabling

[glorfindel]

I multi-table 3 tables on Party poker. I have no problems at first, but after a period of time (@ 1 hour sometimes more sometimes less), the boxes showing the money amounts for players turn clear, and soon after I receive a message that Party Poker has detected an error and to log off and log back on. When I re-boot and log back in, it's fine again for a while. Is this a system resource or operating system problem? Here are my computer specs:

Gateway Select 700
AMD Athlon 700mhz processor
383mb RAM (originally 128mb, and I added 2 more 128mb modules)
Windows 98 second edition
20GB hard drive

I have no more slots available to increase RAM.
I'd be willing to upgrade my operating system if my current configuration could adequately support it.

Thanks for your help.