Have you tried updating to :
Drivers
Speed Passion USB Interface software V1.38 and software
The new V1.38 PC interface have new release 428Stock and 428MOD software, is base on the pass success 323stock platform to improve next step for better performance.
12 Jun, 2012
http://www.speedpassion.net/eu/download.asp?page=1
I've run and still us the GT 2 PRo/LPF.
But don't know the 2.1 version, email or phone call to Schumacher ?