I've had this problem on my iPhone and my iPad now with Spirit JB. Itunes 9.1.1 refuses to recognize the device and says it cannot read the contents so forces me to restore the device.
I've tried JBing on Mac OSX and Win 7 with Spirit with the same results, both machines have iTunes 9.1.1. My iphone 3.1.3 and iPad 3.2 are both working just fine and I can read them in other apps like i-funbox and MediaMonkey.
Any ideas how to fix this for iTunes???