So, I decided to re-install my laptop today.
One thing that got me curious: The NX Client and Sandboxie started showing strange phenomenons.
Sandboxie couldn’t quick-restore files from the sandbox (permission denied error) and the NX Client couldn’t find the default key.
Turns out that both problems have the same root: Cygwin.
After some tries with Try & Decide I pinned down the problem to E Texteditor’s integrated Cygwin installation. Even using the official Cygwin setup and standard install wouldn’t help.
The quick fix for this is to not use an external Cygwin installation in conjunction with these two programs.
Quite a bummer. If anyone has a better fix, feel free to leave me a comment 🙂 .