A customer has a Vista Home Premium laptop which cannot connect to shared 
print queues on an XP PC. This used to work perfectly - I set it up for 
him - but suddenly one day all the queues ("Printer-X on PC-Y") disappeared 
and all attempts to connect using Add Printer fail with "Windows cannot 
connect to the printer. Make sure that you have typed the name correctly, 
and that the printer is connected".
I have reproduced this. What I have established is:

- when Vista searches for shared printers, it lists all the ones that the XP 
PC is sharing

- when I try to connect to one of those printers or select "none of these" 
and fill in the \\pc\printer details manually, the error message occurs 
though without any subsidiary error number

- I can still connect an LPT port to the queue from the Command Prompt, 
using "net use lpt1: \\pc\printer" and then I can print to it using "dir > 
lpt1"

- the same thing happens if I try to access shared printers on another XP PC 
(so the fault is probably not with the original XP PC); unfortunately I 
don't have another Vista PC to try accessing the original XP PC's printers

I've looked on Microsoft's Technet forum and found reference to this error, 
with the suggestion that UAC needs to be turned on. It is: I get all the 
Vista "are you sure" nagging messages.

Does anyone have any suggestions as to what has suddenly caused a working 
Vista PC to start failing? Any suggested cures? I'm still waiting for any 
response to my comments on the Technet thread.