They are right, DFU install is the only way. I used evasi0n last night to jailbrake my iPhone 5 and loved the results. I liked have the 5x5 home screen and even bought the Edgy theme. Then I go to connect to my work email on it (Good for enterprise) when I get a message saying Jailbroken phones are not supported and they deactive my Good client.
Did a restore and it still didn't work. Finally figured out out to do a DFU reset, restored from previous backup, and all was like it was hours earlier minus the lost time.