We're receiving reports that the new title update for Rock Band -- the one that introduced the music store -- is creating some unforeseen problems. Specifically, the patch seems to create some on screen lag not present before the patch. We tested it this morning (we also noticed it over the weekend). Sure enough, there was some lag present and many notes were missed.
Essentially, all the patch does is throw Rock Band's calibration settings out of whack. As the video above notes, the Standard CRT setting defaults to a lag of 0ms. For whatever reason, the patch alters this setting.
[Thanks, Mike McD]

