Cups printing problem solved!
Some weeks ago I mentioned Ubuntu's Feisty was having a weird printing problem that I and many other people reported. It was unclear what was the triggering action and where the fault might be. And it seems it was for a a reason: While everybody thought the problem was in cups code, in the end it turned out the error was on another package. D-Bus is a library that offers a high-level interprocess communication. This library might be used by cups if available. There was a bug on the last version on the library (used by both Debian and Ubuntu) that eventually caused pipes not to be closed properly. The net result was that the cups process was gathering more and more file descriptors till a limit was reached. Thanks to the joint work of many users, Martin Pitt provided a fix for Ubuntu . Your printing blues is over.