dragging them out of the custom.window
works for me

not sure if that works for you too
since you tryed it already ... right?

what happens than?

don`t know if this works in your scenario but I can tell you how I do it and how it allways have worked for me till today without ever having problems at all its this "... drag broush out of custom.pallet.window ..." - thing you mentioned already quite often this is how I delete a brush/tool from my...