#12. "RE: D5000 won't turn on with Sigma macro lens" In response to In response to 11
Hey Ben, I received word from Sigma in NY today requesting that I send in my lens along with warranty info and proof of purchase. They will work on the lens and return it. They feel this is a lens specific problem which would go along with your friend's lens working and yours not.
I will probably send it in but am seriously considering just returning the camera and going with the D90. I'll keep you posted.