Yep, that's common. What is happening is you are arming the car while it is on, therefore the alarm thinks you are still in it and simply trying to arm while driving (this feature is used often by people in high-crime/carjacking areas). When the TT ends it's cycle and shuts down, the alarm thinks you turned the car off and is "letting you out", so to speak. There is a way around this, there is even a fix for it provided by Directed Elecronics (manufacturer of Clifford). Just go back to your installer (I assume it was an authorized dealer) and have them call up the Directed Electronics tech support line and get the wiring schematic faxed over (I used to know it but I haven't done an alarm where someone has had a TT in forever... I forgot the fix!). Shouldn't take more than a few minutes to correct, though. Hope that helps!