Having reinsatlled several machines I have come across a "feature" of the Oracle 9i Administrative Client, it does not play nice and adds its path variables to the start of the $PATH in windows.
This led to much frustration as I *knew* that I had the right version (j2sdk 1.4.2 r10) and it was reporting 1.3.1. CFEclipse would not start and would bomb out with an error reporting an unsuitable java version.
The simple fix to this was to simply add the correct JRE path before the Oracle JRE path. In the majority of my cases it was "C:\J2SDK1.4.2_13\jre\bin" then just run the CFEclipse.exe program and it works!