I've been able to successfully use the NFL app (both Live & Videos) over both 3G & WiFi from roughly August until about 2 weeks ago. I think it was after I upgraded to version 2.5.1 that I found that I can't watch Live over WiFi. To be specific:
I've got a Droid 2 w/Froyo (2.2).
To try to fix the problem, I tried the following with no success:
I've seen a couple of threads around September w/no resolution.