I'm having the same problem. I purchased Rocksmith2014 and Cherub Rock 24875 from Steam as downloads. The program has been working perfectly for the past 3 days since I got it. Yesterday I downloaded a few songs to try installing. I have the p.psarc files and put a couple into the dlc folder. I put the d3dx9_42.dll in the root directory of Rocksmith2014 which is in my c:/program files (x86)/steam/steamapps/common/rocksmith2014. Since the song files have the 248750 id I shouldn't have had to do anything more. When I tested the first one it was in the list, played a sample. I opened it, the tuner came up, I tuned ok then it wient to the playing window with the speakers. I do have sound. But the song never started. I had to alt/f4 to close the program. The second song I used the Song Creator to change the ID number. It went through the process with success but the same thing happened when I opened and tried to run the song. Please add it to the FAQ list as I think it must be happening to a lot more people also. I'm at a loss how to solve this problem.