Rare condition incompatibility of public key

[Myckel Habets]

Hello list,

Last week I had contact with someone who said that my public key was
"bad" according his validation program. I've mailed with many people
before while using this key, but he was the first to tell me that. When
I checked with a friend he said that the key was valid for him.

The key was created in 2005 and at creation time I added an expiration
date of the same day 2 years later. However within some time I thought
this was not really needed, so I removed that expiration date (gpg let
me do that, so I thought it was ok) and kept using that key without any
problems.

Currently my key looks like this:

pub  1024D/9A3D206F  created: 2005-12-10  expires: never       usage: SC  
                     trust: ultimate      validity: ultimate
sub  2048g/D5904978  created: 2005-12-10  expires: never       usage: E   
[ultimate] (1). Myckel Habets (E-mail key) <myckel at sdf.lonestar.org>

The person who said to me that the key validates as bad uses the PGPkeys
program from the PGP corporation software (version 6.58, last version
that was released when Phil Zimmerman worked there, he doesn't trust
later versions) to do the validation.

To sum this up I have two questions:

1) What is causing this problem? Is my key really bad or is this an
incompatibility between PGPkeys version 6.58 and GPG?

2) Do I need to create new keys and revoke this key?

Thank you in advance.

Myckel Habets
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