queston on reportedly invalid PGP signature

Good afternoon all,

I received a message today through the kde-community mailing list, and  
Balsa tells me PGP signature is invalid.

If I explicitly look at the signature part, the first line says PGP:  
signature: The signature is invalid.  The following line is "Signature  
validity: The user ID is of unknown validity."  I expect there is a  
difference between unknown validity and invalid.  The key fingerprint  
does match the key ID of one of the RSA subkeys (using kgpg to  
check).   Two odd things are that it also says "Signed on: never" and  
the "Subkey used" doesn't show any additional lines, whether the little  
triangle points right or down.

So - is there a problem in the signature, or might I have something  
misconfigured?

Thanks for any thoughts.

Jack