ClamAV does not detect EICAR test

[Dave Gattis]

I am setting up a new server.  I have the latest MailScanner and the
latest ClamAV.  When testing with EICAR test files, MailScanner only
reports the usual com and zip file errors.  I suspected that something may
be up with the ClamAV config, so I setup Sophos too.  Sophos detects eicar
every time.  I prefer to use ClamAV.  Any ideas of what I can check?  Why
would Sophos detect while ClamAV does not?
Thanks!
Dave