Many people use OS X to share the services from one system with others on a network, which is particularly useful for small work groups for creating centralized backups, file-sharing locations, and print services. Apple's Server variant of its Mac operating system makes this relatively easy to set up. However, the problem with centralizing services is that if something goes awry then all users will be affected.
Sometimes computer outages such as a reboot or hardware upgrade or a network error can break the connection between clients and services, but at other times a configuration problem from a software installation or a system update can result in services that appear to work properly but keep giving error messages.
Recently MacFixIt reader Mike wrote in with such a scenario:
We have just updated our servers to 10.6.8 from 10.6.7 and all the Epson IP printers colour and mono (mainly C9100/9200 models) on the network are showing "ink/toner waste bin full!!" or "OPC near the end of life" warnings. Although this hasn't stopped or affected printing (as far as I know yet) it's an annoying bug that seems to have been caused by the 10.6.8 update. Other manufacturers' printers on our network aren't affected (i.e. Konica Minolta).
When the 10.6.8 update was initially released, Apple had inadvertently broken part of the printing system causing a number of people to no longer be able to print. Apple corrected this issue by re-releasing the entire update as a version 1.1 release. Because of this issue, my recommendation to Mike was to reapply this update and ensure the software was fully updated, and then try uninstalling and reinstalling the printers with the new software installed.
Sometimes odd configuration problems can be stored in system caches, so often performing general maintenance steps like rebooting to Safe Mode and clearing system caches can fix odd glitches like this. While these are good first steps to take, Mike had already delved further into the situation and found the root of the problem.
The first thing Mike did was take a look at the printer driver configuration on the system. This can be done by going to the Print & Fax (or Print & Scan) system preferences and selecting a printer, then clicking the Options & Supplies button. In the resulting window select the Driver tab and then choose the Select Printer Software option in the Print Using menu.
At this point Mike was able to see a number of duplicate printers, especially for his C9100/9200 printer model. While the system should be able to use only one of the print drivers, if one was updated and the other is an older one that isn't working, then it may have trouble determining which one to use.
The next step was to check the driver files (also known as PostScript Printer Descriptions or PPDs) and see where they were installed on the system. By browsing through the /Macintosh HD/Library/Printers/PPDs/Contents/Resources/ folder on the hard drive (the location where printer drivers are stored), Mike found that the system had one driver file for his printer in this directory and another within a subdirectory called "en.lproj" that also contained numerous other duplicate drivers.
To ensure that the system would use only one of the drivers, Mike removed the driver version from the Resources directory, leaving the one in the "en.lproj" subdirectory. Then going back to the Printer preferences, instead of choosing the Select Printer Software option in the menu he specified the driver by choosing Other and then navigating to the en.lproj directory and selecting the driver version located there.
While it is possible Mike could have just manually selected the driver without first removing the duplicate, this way he made sure that only the correct driver would be selected for use.