Siju George noticed that his mouse would stop working in X, perhaps every hour.  Restarting X would fix it, but he didn’t have a clear cause.  Antonio Huete Jimenez suggested turning the sysctl ‘debug.psm.loglevel’ to 9 to at least see what messages cropped up, and that seemed to fix it.  I don’t think it’s a good long-term solution, but it’s worth mentioning in case this odd bug bites someone else.