Some new info on my issue:
I've set up a brand new installation of FreeNAS 9.2.1.8, 32bit, mirror with 2x 160 GB HDDs and I've chosen "Encryption". OK.
Then I tried following: I saved the "config.db" and the geli_recovery.key and geli.key. I shutdown the machine and installed again a brand new installation of FreeNAS 9.2.1.8 on another usb-stick for start-up.
I've started the brand new installed system, with the already configured HDDs as I mentioned above. I loaded the "config.db" and restarted the machine.
Now I have the same thing as with my productive server: the volume is locked. So far so good.
If I try to unlock the volume with the passphrase, I got the same error as mentioned in the very first post in this thread - it can't be unlocked. But if I choose the "geli.key", it works to decrypt/unlock.
If I detach the volume and auto-import it again, it works, if I gave the passphrase and the geli_recovery.key.
Obviously the unlocking works with only the geli.key or with passphrase AND geli_recovery.key, but NOT with the passphrase only (even if I loaded the config.db). This happens only, if I have a fresh install on the usb-start-stick and load the config.db afterwards. If I reboot the system on the "original system", the passphrase alone, without providing the geli.key, works.
So I guess I don't have the latest geli.key nor the geli_recovery.key for my productive system :-(. Maybe I encrypted it afterwards again, though with the same passphrase, but I got new geli.keys of which I don't have saved a copy as it seems..
Now my question: Is this a bug in FreeNAS? Is there hope, I can recover my data with only the passphrase and config.db, without geli.key or geli_recovery.key? Maybe it's not only a problem in FreeNAS 9.3, also in the 9.2 branch as it seems..
Thanks so much for your help in advance.
P@sco