Custom making, transperancy failed in Thrillix SWF decompiler.

Hello everybody,

I am designing some customs but it seems the transperancy fails in Thrillix SWF decompiler.
I tried to make it transparant in Photoshop, Gimp and Paint Shop but on all the background stay visable. In Gimp the background opacity seems to be changed but isnt gone at all. Also the transparant bar is enabled inside Thrillix.

Does anyone know how to fix this or what program to use?

-Maestro