I looked into this further. Currently a 32-bit JVM is required, however it seems you can have both a 32-bit and 64-bit JVM installed concurrently without any issue (the app will simply default to the 32-bit version… which is why I had overlooked this issue). I also looked at the Arduino source code to see how they are supporting 64-bit Windows and it appears that Arduino for Windows actually includes it’s own copy of a 32-bit JVM that runs locally. I’ll try to add native java 64-bit in a future release. In the time being I hope that installing a 32-bit JVM is not an issue.