Mob spawners went haywire?

I have started a single player map and have been playing on it for about 3 days. There are no mods, additions, or even "God" mode abilities turned on. I recently had a computer crash that was just a complete freeze while I was playing. When I loaded back in, I tried to take a track back to a cave I had been working on and experienced a lot of freezing. I could look everywhere, but nothing would move, and the sound kept going. I eventually restarted minecraft a couple of dozen times and made it back to my cave. I guess this would be the culrpit, but is there any way to fix this, and is there a reason why this happened?