Default printer changes all by itself

We have a 4 computer network just set up with 3 of them connected by Linksys b/g wireless to the router and 1 hooked by patch cable to the same router. Can see all PCs and share peripherals just fine from any of the 4 PCs (all have XP Prof/SP2).

The cabled PC has its default local HP LJ printer change to a remote HP inkjet every time that remote PC prints to its local default HP inkjet. Reset the first default printer back to the local LJ and it changes if the other PC prints to its local inkjet.

Can anyone perform an exorcism?

How many printers and hooked up to what?
Are the printers on print servers or shared from a pc? If a pc, wireless or wired?