Knox has been having a bunch of problems upgrading his Mac to Snow Leopard. After much digging today, he discovered in the system log that startd was complaining about having to throttle cupsd from too-frequent respawning due to recurring crashes. The fix, which is described here, is to revert /etc/cups/cupsd.conf to /etc/cups/cupsd.conf.default.

How annoying that a critical service would crash on a misconfigured settings file! That is non-defensive software engineering. And shame on the upgrade process that mangled the configuration file!

Interestingly, Knox reports that applications that were querying for the default printer were also crashing (OmniGraffle, Photoshop). I wonder whether they all happen to be programmed in a brittle fashion, or whether the system somehow makes them crash when CUPS crashes. Both of those seem unlikely.