I'm guessing it has to do with either the style file or permissions. If you take your reactiontime.csv file and place it in the same folder with some working samples, does it run properly?

I'd try this folder first (from v2010.2.103)

C:\DirectRT\Installation\Source\Files\Main\Compone nts\Samples\2 - Basics\

I think the stim folder there has everything your file calls for. Even the style (.drt) file will accommodate it. If that works, then you could try replacing the style file in that folder with the one from your folder. If that doesn't break it, then I would have to guess it's a permissions issue of some type--esp. if working samples stop working when you move them to the same place. If that is a possibility, could you let me know the full path of your experiment folder?