http://technet.microsoft.com/en-us/library/dd206979.aspx
Disable antivirus scanning of FILESTREAM volumes when it is not necessary (typo removed). If antivirus scanning is necessary, avoid setting policies that will automatically delete offending files.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability