Game Crashing Bug

I am currently in the process of building an adventure map on minecraft snapshot 14w21b, therefore I have a lot of redstone running along with a fill clock which is extremely fast. My issue is every now and then ill notice the game starts to stutter (even though I still have 60fps), because of this I'll close my game however it continues running in the background using around 72% of my CPU and the game stopped saving around 5 minutes before the crash.

I have no idea what is causing this crash however it does seem quite serious hence why I am reporting it. This crash happens at random times and I have no idea what is causing it. I has thoughts that it could be caused by the fill clock however I have used this before and I have never had this issue.

Sorry I couldn't have provided more help,

Mikeey