gpg (GnuPG) signatures on files not recognized by PGP as a valid signature

[paul.healy@goodyear.com]

What do I need to do with gpg (GnuPG) to sign a datafile such that
the licensed PGP product will recognize that its been correctly signed?

* I have gnupg (gpg), remote user has the actual PGP licensed product.
* each of us has imported ( and signed) the others public key.
* The intent is to transfer datafiles encrypting with other's
  public key and signing with our secret key.

This works save for the fact the PGP user always gets the following
error dialog on ALL of my signed file transmissions...

---> File is signed.  WARNING: Bad signature, doesn't match file contents!

the PGP user does infact get my clear text message but they are not assured
that the file is in fact from me and/or not altered.

What do I need to do on the gpg side so that when I sign a data file
PGP will recognized the signature as being valid.

I have gpg (GnuPG) 1.0.6-2
remote user has Pretty Good Privacy(tm) Version 6.5.8