I've had a similar situation a couple of weeks ago (with the version current at that time) - I didn't opt to clear the stats but was in the lucky position to have a maintenance window coming right up... after the reboot things went smooth again.

To me it looked like the "stats update daemon" (whatever it is that updates the graphics) went down for some reason, and rebooting DSS restarted it. Have you done any (more or less severe) reconfiguration prior to the stop of data collection? Maybe some sort of resource change confused the software...

Regards,

Jens