There could be a couple of reasons you get this.
First off make sure you have V 1.2 of robot arena 2 before installing DSL.
you can get it at
http://www.robotarena.comAnoher reason could be because you downloaded the wrong version of DSL TC .. there are two versions , one for the CD bought game you would get at a Store with the box and all. and the other version is the downloaded version you buy online. For some reason files are different in the UI folder and we had to change all the file in the UI folders for each one.
Also make sure you are not installing DSL directly into your robot arena game because for some people there are read only files and the installer will not over write them. Extract to a temporary directory and then move all the file into your robot arena V1.2.
Follow the install instructions in the readme exactly and it will work fine. Don't try to fix the one you have installed it probally is too late . Delete it and start fresh.