OK, I'm rather new about mySQL so this might be a foolish question...

I have now made the import into the beta from UBB.classic, and the forum seem to work (except that I can't access the control panel but that is another issue).

But is it possible to do the import again?
What do I do?
Shall I simply delete the ubbt_ tables in the database and to the installation/import once again?

I have phpMyAdmin installed and I can see an option to delete selected tables. Is it simply to select all ubbt_ tables and delete them and redo everything again?

That would be your safest bet is to delete all of the tables and then redo the installation/import.

Yes, drop tables and re-import - I think I've done it a thousand times now You may need to delete your cookies to be able to log-in to your control panel.