I was encountering something like this, also. When I researched it, it seemed to come down to my attempt to share my printer with other PCs in my house. It was also changing the default "printer" every time I started the PC.
From what I understand, when Vista starts up it looks for printer(s). The first one it finds that fits the description of your printer it sets as the default. If it finds your printer on a PC on the network first, it picks that one. In that, I guess it could then decide that the driver needs to be installed to make it work. The problem I encountered was that even if you are willing to accept printing through another PC to print, it doesn't work.
The only solution I came up with is to NOT share my printer and to eliminate my printer as a choice on all of the other PCs on my network.
I may try an ethernet print server. I found this D-link version on Tiger Direct for $35.
D-Link DP-301U Ethernet Print Server - USB 2.0 at TigerDirect.com
Linear Mode
