Problem getting flats to work

[blinky]

I have around 5hrs on M51 and decided to take some flats (I usually just use DBE!) but for some reason they dont work.  The image is VERY red after processing with the flats and also just seems to mess up the image - like it is applying too much correction to huge areas of the image.
I know its the flats that are causing the issue as if I stack without them its fine.  Here are the files:
FLAT   https://dl.dropboxusercontent.com/u/5236754/Pixinsight/flat-BINNING_1.xisf
BIAS   https://dl.dropboxusercontent.com/u/5236754/Pixinsight/bias-BINNING_1.xisf
STACK https://dl.dropboxusercontent.com/u/5236754/Pixinsight/light-BINNING_1.xisf
STACK Without FLAT   https://dl.dropboxusercontent.com/u/5236754/Pixinsight/light-BINNING_1%20-%20NoFlat.xisf

The camera is a QHY8, I have a home made light box with some white CCFL tubes diffusing light into the box and a piece of perspex to further diffuse the light.  The flats were around 09 secs each and exposed to betweeen 23,000 - 33,000