WordPress has been solid for me for going on 3 years. The other day, for no apparent reason, my scheduled post called in sick. The only message it left was “Missed Schedule.” Um, what? A bit of sleuthing later and the cause was limited to a few things: plugin incompatibility, wonky plugins folder, custom theme.
To fix the problem forum contributors recommend: deactivating all plugins, resetting the plugins folder by FTP or PhpMyAdmin, and/or switching to the Twenty Ten theme to rule out any theme-specific problems. I tried all of these solutions and none of them worked.