Try to get it to work in the following way (worked for me on an iMac 2,4 GHz with 10.5.8 with the same problems at first as stated here):

In the applications (in german: Programme) folder you find the folder Utilities (Dienstprogramme). In this folder start the application Java Preferences (Java-Einstellungen). Under the General tab (Allgemein) you will find two sets of checkboxes. The first ones are for the browser (don't matter for this case) and the latter ones are pro the Java application. See that only one ckeckbox is enabled in here: Java SE 6 64-bit. If that is done a doubleclick on the layout planner software does work alright.

Should you see no such Java SE 6 64-bit checkbox try to install it via the following link (I did so first, so I don't know if I had to or not):
http://support.apple.com/downloads/Java ... 5_Update_1

Best wishes,
Timo (from Germany)

I had similar initial issues, but got it to work: http://www.worldworksgames.com/forum/vi ... php?t=7984

Hi Timo,

thanks a lot. This works fine for me under system 10.5.8 (my office-Mac) but not under 10.4 (my Mac at home). Nevertheless now i can work with the tlx-planner and i will do that at the office....

best wishes from Germany
Uwe