Seeing as you are jailbroken on 4.0, you won't be tethered. There might be some interference with the OS & Cydia. They did just recently upgrade Cydia. I suppose if I were you, I'd respring first. If that doesn't work, turn the phone off, then back on. If that's no good, you might need to try the rejailbreak method. If I remember correctly, the jailbreakme website could work with 4.0. Otherwise, you might need to upgrade & jailbreak some newer OS.