Printer offline

Using a wireless HP 2510 printer, Linksys router, HP machine with XP, and
Toshiba with Vista.
I get everything set up and all work well. Then for some reason the
printer will not work from the Vista machine.
Got to control panel | printers and I see the HP 2510 and it is the default
printer and is "offline".
How do I get it "online"? So far I have been reinstalling it using a
wired link before I can get it online.
Where do I start looking for a solution?