Windows 98/98se explorer

I run a cybercafe with 11 workstations on our LAN.The workstations run on Windows 98/98se. But each time they are being used, they keep giving the following error:

This program has performed illegal operation and will be shut down. Explorer caused an invalid page fault in the module RPCRT4.DLL at 015f:7fc0ec16

Pls, how can I stop this error which is very frequent and always closes all opened and programs prior to the error.

Powell