EFS and SEP11

Occasionally when I try to open EFS encrypted text files on my Windows XP PC, the files are not decrypted and appear to be corrupt. If I reboot, I’m able to access the files again. These occurrences began when I installed Symantec Endpoint Protection 11 MR2.
A review of the Symantec Forums and Knowledgebase isn’t particularly helpful. MR4 is rumored to be coming out in December, maybe that will help. Fortunately the problem is rare. I haven’t had a user reported yet, though I’ve seen this a couple of times myself.