It's a memory error. It could be pretty benign, just a momentary read/write error in memory that's not going to repeat. It could also be corrupt pages in one of your databases. I would strongly recommend running DBCC on them if you don't already do that regularly. It could also be due to hardware issues or even the OS. If you see it again and all your databases have passed their consistency checks, then I would focus on the OS and the hardware.