Do you have the Service Watchdog package enabled? If so, you must not use it for Snort! That is one cause of this problem.
Check to see if you perhaps have gotten multiple instances of Snort on the same interface. Run this command from a shell prompt on the firewall:
ps -ax | grep snort
If Snort is running, you should see only one process per configured interface. If you see two Snort processes with the exact same information and arguments, then you have a zombie running. If this is the case, kill all Snort instances and start Snort on each interface again from the GUI.
Finally, it's possible some particular rule you have enabled is the source of the crash. A Signal 11 error is basically a segment fault (meaning a process attempted to access memory that was out-of-bounds for that process). I run Snort on my personal home firewall and have no issues with crashes. I don't run the OpenAppID rules, though. And there is no guarantee that even if two people run the same rule categories that they have the exact same rule SIDs enabled. So it's hard to compare apples-to-apples when talking about IDS/IPS setups.