What is the IBM running for a wireless NIC?
Start> Run> NCPA.CPL>Right click wireless network connection, left click properties > Copy from "Connect Using" field.
It could be a setting the advanced options, but I suspect your instinct is right. If your new laptop is G, and your old is B, then its probably a band issue. You can start tweaking some things, like CTS legacy support or setting it to a static channel, but at a cost to performance on the new laptop. May be minimal loss, but most likly some loss.