[mithrandir321]

Okay, many thanks for that one, musnake. I checked it out with this result.

.htaccess was full of old paths and updating solved the 500 internal server error. But it didn’t help much in the way of the database errors and I didn’t find any old path references in the DB nor in any files.

So, while queries into the DB for topics and forums is okay, the only thing that doesn’t work is the users (my BB homepage when asked for any user data gives the above errors) – which is taken from WP shared table. So could it be that the error is in initialization global $bbdb; ???