Invalid packet error message

[DUELL, BOB]

Hi,

When trying to decrypt a file, we are getting this error message:

   gpg: [don't know]: invalid packet (ctb=70)

Does anyone know what this means?  I tried several Google searches but can't find anything relevant.  FWIW, here is the command (all one line):

   gpg --homedir /opt/app/apps/dbmprod/gpg --local-user "mykeyID"
   --output imdm_extract_20121221.dat 
   --decrypt imdm_extract_20121221.dat.pgp

Thanks,

Bob