Help needed: Two keys for two different e-mail adresses

I migrated a User from an older to an newer Mac mini Computer. I also installed Symantec Desktop Encryption 10.3.2 for use with Mavericks.

The user before used Version 10.2.1MP3 under OS X 10.6.8.

There are two e-mail adresses sending/receiving configured with PGP Messsaging.
Under the old system everything worked just fine.
In the new environment, the second key is not even visible for use with Messaging :(

How the heck can I re-install that second key for use with Messaging??

For the time being both e-mail adresses use the same key but the recipient always gets a message saying that a "unmatched key" was being used - which is obviously true.

I would appreciate any help.

Peter