On a 64-Bit Windows Vista system, install Java 6 update 12 and remove all other JREs. Install Java FX SDK 1.0 - the installer cannot find any Java so it wants to install JDK 6 update 11. If you skip this step the installer does not complete successfully and you cannot build FX projects correctly.

I'm pretty sure the problem is that Java 6 Update 12 installs itself in C:\Program Files\Java\... instead of C:\Program Files (x86)\Java like previous versions. The FX SDK installer expects things to be in Program Files (x86) for some reason and can't deal with this situation.

I think the installer script needs to be more robust when looking for installed JREs and JDKs, especially on Vista.