Yesterday I encountered a rather odd issue at a customers site, whereby the storage service seemed to have gone a little bit, well, how shall we say ... mad?
After a little bit of troubleshooting I happened across this particular article on Symantec's knowledge base:
We were indeed seeing lots of the 6656 and 6654 error-pairs throughout the event log. In the end the only thing that fixed it for us was a system wide reboot across 4 different EV servers.
Very odd, but so far (touch wood) we've not had the same issue again.