Vista - Unable to print to Shared Printers on Windows XP Pro PC

I have a Home Workgroup consisting of a Dell Vista Home Premium PC and a Sony
Vaio XP Pro PC which has 2 shared printers attached to it.

I have mapped my Dell Vista Home Premium PC to my XP Pro shared HP Laserjet
1300 & HP PSC 2400 by using the UNC and not the Printer Wizard (It didn't
work at all). At that point the XP machine sharing the printers shows up in
the Network folder. I then installed the appropriate printer drivers on my
Vista PC. At that point, I was able to print test pages to both printers.
However, when I rebooted the Vista PC, I am now unable to print any more. I
either get an "RPC server unavailable" error or the document just sits in the
print queue till I cancel the print job and then it is gone. The printers
still show up in the Printer folders, but I can't print to them any more.
Also, the XP Pro PC no longer shows up in the Network folder. I have
followed all the procedures on Vista's website pertaining to Sharing Files &
Printers between XP & Vista machines to no avail.

Can someone help me out.

Thanks.