[RHEL5] Cannot export a private key created with Gnupg 1.0.6 on RHEL2.1.

Issue

• Our customer tried to import a private key created with Gnupg 1.0.6 on RHEL2.1 to RHEL5.7(Gnupg 1.4.5) environment, but it failed (0-byte file was created as a private key for RHEL5.7). A public key was created correctly. He exported the private key again on RHEL2.1 and tried the same operation, but the result did not change.
• Isn't there compatibility of the key between RHEL2.1 and RHEL5, or is it a bug?