freebsd stable - Jan 2008 - Big geli proglem: MD5 hash checksum mismatch for da0

Hello,

I tried to change my passphrase for a geli provider.
Like man page tells, I attached the provider (da0) and used
'geli setkey da0' to change the key (only one key, no keyfile used).
Everything seemd to work but after detaching any attach attempt fails with:
MD5 hash checksum mismatch for da0

What went wrong? And how can I solve it? Needless to say that it's
important data and I really don't hope that geli was corrupting it!

Thanks,

-Harry