The only thing in System > Log is the app restart afterwards. No errors that I see before hand.
Event Viewer shows (which is right around the time of error/site down):
A worker process with process id of '7712' serving application pool 'DSP Site' has requested a recycle because the worker process reached its allowed processing time limit.
Not 100% sure, but I believe this was triggered from some settings I set in Application Pools > Advanced Settings > Rapid-Fail Protection
Current settings there are:
Service Unavailable Response Type: HttpLevel
Failure Interval (mins.): 1
Maximum Failures: 5