I deleted, uninstalled everything and checked the box for the portable installation. Now it works, but this seems like a pretty big bug that I can't believe the developers don't care about.

I had the same problem. Tried a lot of things. Eventually got the last 3.x version from FileHippo and installed it. Version 4 still had the troubles, so I just kept hitting "Ignore". Eventually the messages went away and the program started working.

mediamonkey.mdb is from MediaMonkey 2, MediaMonkey 3 uses MM.DB, although I'm not sure what the name of the backed up db is.

I deleted the database, at least I think I did. I deleted the mediamonkey.mdb file. Is the database file different?

Eli wrote:Don't know why re-installing MM3 and upgrading again would be helpfull.

You may have database errors in your MM3 database that cause problems in the upgrade from MM3 DB to MM4 DB. Installing MM3 and running "File > Maintain library > Optimize database (complete)" could fix these errors prior to the upgrade.

I CANT open/start MM4 to do ANYTHING.

I have uninstalled MM4 and deleted the MM DB and reinstalled. Don't know why re-installing MM3 and upgrading again would be helpfull.

Try to use the maintain library feature at File > Maintain library > Optimize database

If it doesn't work in MM4, reinstall the last version of MM3, try it, and then upgrade again.

I just installed MM4 to give it a spin. Install seemed to go fine, but when trying to launch I get the following error msg:

There was a problem querying the database:
Error executing SQL "DROP TRIGGER update_song_artist
" : no such trigger: update_song_artist (1,1)

I tried uninstalling and deleting the database, then re-installing. Same problem.