Maybe this is relevant:
I only installed gpg, gpgEX and GPA from the GPG4Win package.

Using gpg.exe on the command line works perfect.
I can en- and decrypt files and sign and whatnot.
Only gpgEX is affected.

The crash happen regardless of what I did before. Usually I use Q-Dir as file
browser. When I trigger a gpgex action via context menu in one Q-Dir OR Windows
Explorer the program (the one I used) crashes.

I set GNUPGHOME as a user variable via Windows' Extended System Settings.

I followed Bernhard's suggestion and attached the GpgEX debug log.

Actually, I can't.
The link you provided leads to a site with some general infos.
There is another link into the compendium with infos about
some GPG4Win components but not a single word on gpgex.

So HOW do I provide some more diagnostic output?