I know of this problem and, albeit, a new release of MTU programs is ALWAYS welcomed, the work around is rather simple. Whenever you have had a problem just remember, if Windows is always looking for the program software in the folder c:\Windows and you move the program files to c:\Programs unless you tell Windows to look in the new place, it won't. It will ALWAYS use the old files until you change it.
As I don't program, and I don't work for MTU
I have NO CLUE how to re-program the software for where to look... THEREFORE, if I always install what I need to where it should go (avoids this bug). Whenever you delete (or need to delete something) delete the mdb file from c:\Program Files\MTU\Hoster\Databases. Then AFTER you have deleted all the tracks and reimported all the tracks you want, rebuild the database and make sure you save the database to the SAME place above.... It should ALWAYS work.
IF you don't save the NEW mdb in the right place I THINK that MTU has a back-up of the last saved file somewhere and it reverts back to this. So, make sure that the file is stored where it needs to be.
Hope this helps