So I've been mining slush's pool using GUIMiner and getting about 25Mh/s with my GPU.

As I am starting to understand mining better (still a complete newb) I decided to give eligius a try using BFGMiner (I'm running a Win 7 - 64bit machine.) The problem is that running BFGMiner I am getting less than 10Mh/s. What am I doing wrong?