[CentOS] crashes during raid-check

For two of the last three sundays, my desktop crashed overnight, apparently during the cron raid-check started. Has anyone seen anything like this? q

The last message in messages tells me the syncing operation started. Within minutes, the machine just quits. Other weeks, the sync completes normally, with no problem reported in a couple years of operation. . 

I've disabled the cron.weekly job until I get a chance to run it manually..

This is a software raid 1 with two 1.5 tb drives. 

My prime suspect in all mysteries is the nvidia driver but I have no clue. I use kmod-nvidia from elrepo.
Thanks,

Barry