OS - Windows, Solaris, Linux
Browser - Mozilla
build - Any mustang build

Open any applet in Mozilla, and open the java console
Press s for all the system and deployment properties

Under deployment properties, "deployment.browser.path" value is wrong. It does not show the location of the Mozilla browser being used. Here is what is displayed for each platform -

All Windows - It shows the path for the Internet Explorer

Solaris and Linux - It shows a different path, depending upon the OS and the set up you ave
For Linux Cinnabar - /usr/bin/mozilla
For Solaris 10 - /usr/sfw/bin/mozilla
For Solaris 9 - /usr/dist/exe/mozilla