Problems with keys

[Martin Taylor]

I have recently installed GnuPG 1.2.4 on a Windows XP SP1 system, and am 
having problems. When attempting to import a key (using GPGShell v3.10), 
I get the following message:

gpg: [don't know]: invalid packet (ctb=2d)
gpg: read_block: read error: invalid packet
gpg: import from `C:\Documents and Settings\Martin\My 
Documents\Non-RE\PGP\msrc.
asc' failed: invalid keyring
gpg: Total number processed: 0

The keys concerned should be totally valid: they were previously 
installed on a Nullify 1.2.2 build. I have also confirmed the problem by 
downloading Microsoft's public key: same thing happens.

I am able to generate a new key, at least.

Does any possible cause for this problem spring to mind?
-- 
Martin Taylor