The problem is reported to stem for the large amount of traffic, much larger than the system could actually take. A post on the Guitar Hero forums reads the following:
“The launch of Guitar Hero III has produced heavy amounts of traffic to the website, and this traffic has caused a number of users to have problems with linking their accounts and uploading scores.
We are well aware of these issues, and we our working as fast as we can to fix both problems.
You can still play through GH III, and rack up as many high scores as possible, and those scores will be displayed when we smooth things out.
We appreciate your patience.
Keep rocking out in GH III, and check back for more updates soon!”
Guitar Hero III: Legends of Rock was developed by Neversoft and was released on PlayStation 2, PlayStation 3, Xbox 360 and Nintendo Wii.