We have our QA files on a machine running XP being used as a server.  A few months ago we suddenly got errors of something like "can't find network drive" from the various machines accessing that.  We were able to check the error message and Microsoft's on-line tech info said a particular update could cause that.  When we uninstalled the update on the XP machine everything worked fine.

A related possibility is that even if you uninstall a printer, Windows 7/8 doesn't automatically uninstall the associated driver.  On a number of occasions, in troubleshooting a printer problem I uninstalled and reinstalled the printer and it didn't help. One time I noticed that after the uninstall the driver was still there.  When I uninstalled the driver and then reinstalled the printer that fixed the problem.

How many updates have there been since the problem arose?  Are any specific to printers or to a particular brand or model?

One technique you can use is called "half-split division".  Imagine that you have a string of 100 lightbulbs and you don't know which one is dead.  You can remove #50 and check continuity from 1 to 49 with one test.  If that's good, you've eliminated 49 with one test. If that's bad, remove #25 and then test from 1-24 (and if necessary 26-49).  Then remove #12 and repeat.

The same thing can be done with adding back the updates.  (By the way, I would first try reinstalling ALL the updates.  Sometimes sequence makes a difference and the problem may not reappear.)