For the last week I've been getting "Startup disk is almost full" messages, and spent a lot of time cleaning house, only to have it nearly full again the next day.

The X Lab suggests looking at the console logs to see if there are any log files that that are growing out of control because of runaway processes. Sure enough one file was huge: 12.5 GB, filled with errors generated by a dashboard widget, Plazmatunes.

The log files and Plazmatunes have been deleted. Now I'm waiting to see if this ever happens again.