If I download a map and drag it into osu!, it just goes to the song selection screen, but doesn't add the new map to the list.
I reset osu!, and it gave me a message saying that the beatmap database appeared to be corrupt, so it had to rebuild it from scratch. Still, it didn't work.
I checked the osu! folder, and found that there were some read-only files in there, so I undid that... and nothing.
I'm running 64 bit Vista on an administrator account.
Anything else you need to know?
Reinstalled, everything's hunky-dory. LESSON LEARNED: DON'T CLICK FORCE FOLDER PERMISSIONS!