I have a 2008 Ford Escape, A new transmission was installed 8/2012?

I was at stopped at a red light and when it turned green and I accelerated the car did not move forward. It did not feel as it was stuck on first gear, it was more of a powerless feeling to it. I got it into a shopping center by putting the vehicle in reverse. It had no trouble backing up. What do you think is the problem? Can it be the transmission again? In the past, when the transmission had to be change completely the car was kind of stuck on 1st gear. This is totally different, it is as if it had no force to move forward. I still have the warranty from when the transmission was changed, it has been 30,000 since the new transmission was installed. Please help me. The car now has to be towed and I don't know if to get it towed by the transmission people or to my mechanic. Can it be something not related to the transmission?

Its doubtful the new one would still be in warranty after 30k but I would at least start with the shop that replaced it. You don't have to have repairs done there but they can at least give you an estimate of repair. It could be something other than the transmission itself but you're going to need a shop to diagnose it. You have checked the fluid level haven't you?