Sudden network issue moving from hub to switch

I recently moved a lot of our 98 2nd edition clients to a cisco switch and removed an old hp hub from our network. All of a sudden, many 98 clients are receiving a no domain error when they boot. Typically the users can hit cancel, and try to login again and they can login successfully. A few try rebooting until they login. In all cases, they are able to eventually get on the network without switching any of the cabling. I have updated the 3com drivers on the nics which are typically 3c905c or 3c905b-tx, but that does not eliminate the error.
Does anyone know why they would not recieve this error on a hub but suddenly see it on a switch? (Our domain controllers are connected to the same switch.)