Hi Steve,
I actually only did what I wrote in the post. I downloaded and installed the JRE 64-bit RPM (not the JDK but that doesn't matter) in a clean install of Centos 6.2 64-bit. This Centos version comes with with Firefox already installed, no need to play with symlinks and such. As for the JRE installation. The RPM does all that for you. Again, no need to change any settings.
Then I installed Servoy 6.1 in my home directory and ran it without any problems.
In short, I ran 2 installers and it worked.
Perhaps you have been tinkering too much with your system and it's no longer in a sane state?