Sudden problem with sharing wifi printer.

My all in printer is an Advent Premium WiFi AWP10. I have used it OK
for a couple of years sharing between an Advent 4211C Netbook (wifi
connected) and a Novatech Desktop (usb connected). without warning a
few days ago the netbook wouldn't connect with the printer. I checked my
router pages and found that it seems to be connected there OK, both the
netbook and desktop will connect together (wifi) and share files and
folders OK. I have reset the printer, re-installed the printer
software on the netbook, all to no avail. I have set up the printer on
the netbook for a usb connection and that works fine, but when trying
to set up for wifi connection the netbook just won't find the printer.
Strangely pinging the printer's IP address from both netbook (wifi) and
desktop (usb connected) time out.
I'm sure that rectifying the problem must be something quite simple,
but I don't have the knowledge to sort it out. I should have said that
both netbook and desktop are running Windows XP Home Edition, service
pack 3.
Has anyone any ideas what is amiss, and an approach that I should make
to rectify the problem. Hopefully an idea that is better than just 'get
a long usb lead for the netbook' will be suggested.
TIA