gpg/pgp interaction question

I've got gpg 1.0.1 set up and it's working just fine with another gpg
1.0.1 install, but I can't verify a clearsign from a pgp 6.5.3, and it
likewise think's I'm hosed.

I've perused the mailing list and the man page to no avail. I thought
before I dropped a note off to the gpg mailing list, I'd ask the local
heads about gpg.

Ideas?

TIA,
David