Wierd Network Printing Problem

I am running a home network with 3 PC's & 3 network HP printers.

2 of the PC's have started to experience problems printing in that documents
sent do not print, they just sit in the print window (figuratively speaking).

There seems to be nothing wrong with the network as after documents are sent
to print, I can ping the printers & also log onto their admin page via a
browser using their IP address.

The print spooler is running, but if I re-start it, the documents print.

This is driving me nuts. Does anyone have any suggestions?

Thanks in advance.