RDM hangs while running a hta file

Hi,
I created a session for the Skeep ( http://www.skeep.co.uk/VNC/ ) hta file.
The hta itself runs just fine. But RDM seems to get no info back and hangs while the hta is opened.
After the hta file is closed, RDM works a little and prompts an error "Unable to execute the application!: "C:\Program Files\Skeep\bin\svnc.hta"
So, while the hta is opened, RDM is not usable until you close the hta.
To start the hta, I had to select "Use ShellExecute" in RDM. Otherwise I get some "Illegal character in command-line".
Entering the Process name "mshta" didn't helped me so far.
Best regards
Steffen