I have a Dell MFP 1815dn and am running Win 7 64 bit, but I had the same problem with this printer on XP.  This is a networked printer, so both the desktop and 2 laptops use it.  The printer frequently shows as "offline" on the laptops and will not print.  Nothing we can do seems to reset it -- we end up rebooting both devices several times until it finally works or, if that does not work, uninstalling and reinstalling the driver.  Obviously that is not a workable solution.

I can't find anything on this problem -- what does "offline" mean, and how can I get it to stop going offline, and how can I get it back "online" when it does?

Any help much appreciated.