The Gizmodo crew has been busy playing the hell out of Guitar Hero 2 on Xbox 360 and we are indeed encountering the problematic whammy bar. Luckily instead of taking the guitar back (and have to look like a moron carrying a fake guitar across town) there is a handy DIY fix to the non-responsive whammy bar.
All you have to do is crack the guitar open, loosen some screws, rotate a unit, and whammy (pun intended) you are ready to go. I'll probably be doing this rather than having to take the unit back or—gasp—RMA'ing the unit and having to go without my beloved GH2 for days. Hit the link below for instructions.