Previous Weekend (Not Last Weekend) Pearl Reset

The prior weekend, I woke up Saturday morning to find that the BlackBerry 8100 had reset. The PIN and key were still there, I could still send and receive emails. However, all the emails in my Inbox and all the calls in my call log had been cleared. Weird. I don't know if the device somehow ran out of memory or what, and then reset those areas or what happened. However, everything seems to still be working a week later.