Recently, Sun upgraded the Java JRE to version 1.5 We are working in testing our software with this new version. In the meanwhile, we encourage our customers to use Java JRE 1.4.2 to run the software. You can get this JRE here.
The Panel Planner Windows Installer searches for JRE 1.4.x in your machine, and proceeds only if it is available.
You may have both JRE 1.5 and 1.4.x installed in your machine.