Having a problem with encrypting and decrypting files.

[Timothy Nam]

I was wondering if somebody could help shine some light to a problem I am 
having.

I have a public key generated using version 1.0.7 (SunOS) , the 
counterparty I am exchanging keys with is using version 1.2.1 (MingW32). I 
have imported his key, as well as him importing mine, but when I try and 
decrypt a file which is signed and encrypted by the other party, I get the 
error 

gpg: decryption failed: secret key not available. 

Is there a compatibility issue with the versions we are using? 

regards

Timothy (Ting) Nam