I tried this again and it looks like I’m stuck at the same place.
Rock Band 3 gets stuck on “LOADING NEW DOWNLOADED CONTENT… 351/351 LOADED”
You must have an error in your songs.dta file.
How many custom songs did you add? If it’s not a huge number, we can check your songs.dta and figure it out.
You are about to leave Rhythm Gaming World and access the external songs DB. While no song or file sold for commercially available videogames is hosted there and only fan generated content is allowed, Rhythm Gaming World has no direct control over the database and no files are hosted here. Alright, we had to made you aware of this, now you can visit the database!