The Mac OS X 10.6.8 update may cause problems printing to network postscript printers. When this happens, the printer queue on the Mac remains in a permanently paused state, and nothing can be printed.
This issue has something to do with changes Apple has made to SNMP in the CUPS backend. It has been confirmed to affect printers from various vendors, including: HP, Canon, Lexmark, Konica Minolta, Zerox, OKI, and Toshiba.
There are three workarounds that have surfaced to this problem, in addition to reverting to Mac OS X 10.6.7, but ultimately everyone is hoping Apple will release an official fix for it.
The first workaround is to edit the PPD file for the printer(s) that aren’t working, adding a *cupsSNMPSupplies to the end. The process is summarized here: http://fieryforums.efi.com/showthread.php/2406-OS-X-10.6.8-Update
The second workaround is turn off SNMP on the printer(s) that aren’t working. For some printers this can be done on the printer’s control panel, others require logging into the printer’s web administrator interface. This workaround may however lock out the printer’s web administrator interface, or cause problems with older Windows computers printing to the printer
The third workaround is to replace the contents of /usr/libexec/cups/backend with the contents from a Mac running 10.6.7, or using Time Machine to roll back the contents of this backend folder from a pre-10.6.8 state. An unidentified developer from Japan has posted an easy to run script that replaces these backend files, downloadable here: http://www.geocities.jp/horiemonmail/Repair10.6.8.dmg
It is unknown if these workarounds will cause a problem if/when Apple releases an official fix for this problem, so therefore Techcare considers them as use-at-your-own-risk, and we will not be pushing out the Mac OS X 10.6.8 update until the dust settles with this issue.