http://dev.mysql.com/doc/refman/5.1/en/news-5-1-12.html:
Incompatible change: Support for the BerkeleyDB (BDB) engine has
been dropped from this release. Any existing tables that are in BDB
format will not be readable from within MySQL from 5.1.12 or newer.
You should convert your tables to another storage engine
before upgrading to 5.1.12.
One down, one to go?
Regards
Ian Barwick