I have also seen weird issues when the users have a lot of printers, mainly if they are not connected. I remember I had a user that had several "weird" issues, so I deleted all the printers but the 2 he used and he never had the issue again.
Another issue that I run into was a computer that would restart when the user needed to print. That I think it was caused by a conflict of I/O in the USB ports. I deleted all the printers, re-installed the drivers and connected the printers again (switched the USB ports to force detection as well) and then the problem was fixed.