A few OS X users who have upgraded to Lion may find that certain printers they have installed may pause when print jobs are sent to them. The printers are still installed as they were before upgrading, and print jobs will spool to the printer queues, but once in the queue, the job pauses.
Some people have found this to happen with certain networked Xerox printers, but it may happen to others as well.
It turns out in some instances the OS upgrade process may reconfigure printers to use a different connection protocol than the one that was designated before installing Lion. For instance, it may switch to using Bonjour instead of a directly IP connection.
To fix this problem you will need to delete the printer and then reinstall it using the desired protocol and settings, which can be done in the Print & Scan system preferences. Select your printer and remove it, followed by clicking the plus button to add it to your system again. Then choose the connection type (use "Default" for Bonjour setups and direct connections, or "IP" for direct network connections), and then configure the printer's protocol, address, and driver.
If the printer still shows problems after this reconfiguration, then try right-clicking the printer list and choosing the option to reset the print system, which will clear all the printer configurations and set the system back to default settings. From here you should be able to set up your printers again.
This is likely all that is needed for systems experiencing print issues in OS X Lion, but if you are running Snow Leopard and are experiencing print problems, then you might try downloading and applying the latest Combo updater for OS X 10.6.8. In Apple's initial release of 10.6.8 a misconfigured component of the print system resulted in printers having pause problems, so Apple released a version 1.1 of the combo update (found here) to in part address this issue.