NNPAS crashes domino

I’m running symantec mail security for domino on a windows 2003 server sr2 X64. nnpas process crashes domino daily. I upraded to the latest build of mail security as there was known isssues with v 5.1.0.25. Unfortunately, I still have crashes. Could this be attributed to the 64 bit architecture? Is anyone else having problems with 64-bit platform.