I've downloaded updates of songs I've been playing for a year ( The Strokes) and recently downloaded songs (such as The Undertones). Prior to downloading the updates I could play them but once updated I cant launch the song in the game from the learn a song or  non stop play mode. As a total idiot , when it comes to computers, can anyone offer a solution

cheers

make sure you don't have duplicate songs... for example, if the update has a different filename. Don't put both version one and version two in the dlc folder.

Re Apply the app id. For some reason,, even though it is the right one,, you sometimes need to redo it. You can do this with the Rocksmith Toolkit. Available here. http://www.rscustom.net/ . Also check this thread, the APP ID process is the the same. http://customsforge.com/topic/10000-song-not-showing-up-lets-fix-that/

make sure you don't have duplicate songs... for example, if the update has a different filename. Don't put both version one and version two in the dlc folder.

Also, when you update a song to a newer version,, it will not overwrite the old version. The file names are different I.E. V1 V2,, so on and so forth. So if you don't remove the old one it WILL cause a conflict. We call this the same name issue and there is NO fix. Hurt from NiN and Hurt from Johnny Cash cause this. It's a limitation of the game and so far this really can't be fixed. Make sure you only have the newer version in your DLC folder. If you DID delete the old one then change the APP ID and that will fix it.

thanks a lot for all your help :D