Nothing has changed like downloading XP SP3 or switching to Vista, right?
Is it attached via USB or parallel port? If USB, try connecting it to another USB port. If that doesn't work, I'd try another cable. If that still doesn' t fix it, then there could be something wrong with the printer. ("could", not necessarily, but "could")
If it's connected parallel, then I'd try another cable.
If neither of the above fix it, then I'd delete the printer, download the latest driver from HP, and reinstall manually. Don't do the wizard where you "add new hardware"....go to printers and click "add a printer" and install it that way. When it comes to driver, click "have disk" and point it to your C drive where you installed the recent driver.
If after all of this is done, and still nothing, then it could for sure be the printer.
This is HP link with latest drivers. You'll need to select which one you have. It should be on the front of the printer.
http://h20180.www2.hp.com/apps/Lookup?h_lang=en&h_cc=us&cc=us&h_page=hpcom&lang=en&h_client=S-A-R163-1&h_pagetype=s-002&h_query=HP+PSC+1400&submit=Go+%BB