Problem with tilesets

[Jonathan]

I have been getting a small bug when i try to add my own tilesets in, i did convert them to BMP and add black background to them, but when i put them in the MASK layer doesnt take out the Black (0,0,0), i am using MS4 and only seem to get this error with these tiles. I attached a zip of the original unconverted sets if anyone else wants to try to help me out...

http://osenia.no-ip.biz/Tilesets.Zip