I jailbroke my iPod touch 4.2.1 with greenpois0n and it worked, but when I used the loader for Cydia it only partially downloaded! I did not touch it while it was installing and now there's a blank app labeled Cydia. But when I try to open it it only comes up for a millisecond then exits out. Yes I rebooted my iPod and tried to reinstall it with the loader app but it didn't work it said that Cydia had already been installed. I tried to delete it but no x appeared on the upper right hand corner. Please help!