I had this issue, my share name is different them my printer name. When i changed the name to my printer name it worked.

example = SetDefaultPrinter ("\\printerserver\hplj4")
that did not work

under the general tab of my printer properties the printer name was "HP Lasterjet4 - 2nd Floor"

When I changed my code to SetDefaultPrinter ("\\printerserver\HP Lasterjet4 - 2nd Floor") it worked.

Hope this helps someone.