Missed second!!!

Ok so I pull up to a light after just filling up with gas and these to guys in an old chevy truck jump a little to try and race, so I give them the thumbs up, and roll down my window and answer their Qs about what kinda of mustang it is, then the light goes green so we both punch it.I pull ahead through 1st, the when I try to drop second, the freekin tranny STOPS me right before second (no grind, just stops) so it revs to like 6K and then I am like trying to get it to go in, then it decides to let it go and I squeel 2nd pretty good with the high revs...even though I still murdered the truck, it made me freekin mad. So I decide to try again down the highway, slow roll in 1st, nail it try and shift to 2nd, DOES IT AGAIN!!!Just stops.So I slow down and have another go at it, run through 1st SLAM it and this time it goes but almost stoped me again, even twisted my nob making it go(still hit 3rd though LOL).So whats with this???Is this some freek thing where my trans screwed me over, and made me look like an idoit missing 2nd or is this some tranny problem, like that grind thread? This is the FIRST time to miss ANY gear when speed shifting after installing the pro 5.0 and have only messed up once before when cruzing when I went from 4th back to 3rd at low RPM when trying to hit 5th.I am going to try this 1st-2nd thing again in the morning when I go to work.Jeeze this just eats me up for some reason LOL.BTW there was a cop just after I raced that truck, I let off at about 50-55 in a 45.Pheew. Thanks for any help guys.