Not much of a TAG guy these days, but you might want to check your clutch condition/settings . Are you running the EXPD or shoe type clutch? We had a similar problem at the Robopong (Roberto!) and it turned out that one of the shoes had broken – at speed you’d never notice the problem but really, really hard to get going, if at all.
We may not be the fastest on the track...but we're having the most fun!