I was letting the arrow back down,(IE unwinding the cocking mechanisim) and the release block popped (just like it has so many times while cranking the arrow into the loaded position). YES, just like you are thinking the arrow fired
It sounds like you are describing something that's happened to some others, where your cocking block jumps forward while you are cocking or uncocking.
One possibility - your cocking string needs to start winding in a certain direction, otherwise it all stacks up on one side and eventually drops off the stack causing the jump. The last page of PSE's instruction manual talks about the fix. Here's what it says:
When cranking, a clunk is heard and the arrow may pop off the string.
The draw cord is not spooling up properly. The draw cord is initiating its spooling in the wrong direction. Looking at it from the back it should spool to the left first. Remove the lower and unspool the release all the way. Start cranking it back and use your finger to start the spooling in the proper direction. NOTE: When pulling the release forward, only pull it far enough forward to attach it to the loop. This will prevent the first wrap around the spool from winding in the wrong direction.
If that doesn't end up being the problem, I've repaired a few that have had one of several small parts inside the guts of the cranking mechanism fail and need to be replaced. In that case, get your bow serviced.