I am using AutoHotkey version 1.0.47.04 under VISTA, may be this is the reason why it works in my case.
AutoHotkey help contains some hints into this direction:
...
One True Brace (OTB, K&R sty ...
This miraculous script also solves some "old" problem discussed in
http://www.autohotkey.com/forum/post-164741.html#164741
which is to save an image in the clipboard to a file.
See impecc ...