Database query calls wrong DB instance!!

[eluser]Swedie[/eluser]
I have encounter a very mysterious problem that I cannot debug.

On my local test server things are working as expected. On the production server, with the exact same Apache, PHP and MySQL, CI apparently tried to run a query from another instance than the one I'm doing the query through.

The query fails with CI saying it can't find: databasename.sometable.

My application is a controller and lots of models.

I've run print_r on both the complete CI object and the DB instance and the database settings are all correct. But when running the query, CI for some reason is digging in the wrong DB instance and thus not finding the table.

What can be causing this?