Hello, I do have the same problem:
"Warning - Problem running post install step. Installation may not complete correctly
Error running C:\opt\OpenForisCalc/R windows/install.cmd
C:\opt\OpenForisCalc/R windows/: Das System kann den angegebenen Pfad nicht finden [system cant find the path]".
Here the specifics requested by Mino:
R version:R-3.1.2-win
Jdk version: jdk-8u25-windows-i586
PostgreSQL version: postgresql-9.4.0-1-windows
Operating system: Windows 8.1 Pro; 64bit on Lenovo Yoga
Path where R is installed: "C:\opt\R-3.1.2"
Path where Calc is installed: "C:\opt\OpenForisCalc"
Path where PostgreSQL is installed: "C:\Program Files (x86)\PostgreSQL"
Appreciate your support! Thanks Ulrich