First time at the itunes store, i downloaded my first app, "Predators" it downloaded to itunes but won't sync to my itouch. I followed the troubleshooting guide on the Apple support section, checked that my touch OS was compatible (3.1.3) etc etc, but when i try to sync, i get various messages, "will not sync due to invalid signature", "failed to sync error code 0XE000004. Tried deleting and reinstalling the App and itunes. I was able to download and install a FREE app. I also, put a post in…See More