PMK - Are you running at Tim's new track? The surface there is very unusual and you may want to try a different rear tire to reduce traction a bit. Old fashioned Green Dot foam might be the way to go.
What traction compound are you using? IF you are using Paragon or some other "real" traction compound you might be getting too mush grip out of the tires. Try some Coppertone Water Babies 45. Coat the rear tires, let it soak in for as long as you can, the longer the better. Wipe it off with a tire rag until the tires are all clean (they may still feel slick, thats OK) ands go race. The suntan lotion will give more moderate, more consistent traction than "real" traction compounds.