Hi Andrew,
Thanks for reporting your issue.
We're able to reproduce the problem, and have identified it as a bug.
While we work on fixing it, please use one of the following workarounds (which you've already found, I suppose...) for the time-being:
1. use the full-path to qube.exe, as in: C:\Program Files\pfx\qube\bin\qube.exe
2. launch the GUI in the bin directory, as in:
cd C:\Program Files\pfx\qube\bin
qube.exe
Sorry for the trouble, and let us know if you need further assistance!
-shinya.