I don't know how much help this will be, as I've unfortunately not had any experience with the Galaxy S series or the Kies application. However, I'm quite familiar with the Samsung Moment and the myriad of issues surrounding drivers and software running natively in Windows to flash that device.
From the Linux end of things (Ubuntu x64) I was able to get the software for the Samsung Moment (SWUpgrade, it's called) running through VirtualBox on a Windows 7 client from the Ubuntu host. Took me a good couple of hours to get it working, and even still, it's a bit finicky at times, but I've successfully flashed my Moment several times from Ubuntu using that rather thick layer of virtualization.
I don't know if that would be a feasible option for your setup, or if the software would even work the same, being a completely different phone. I would imagine the software would be somewhat similar, as they're both Samsung devices and most Samsung devices do share similarities when it comes to the proprietary file system and partition structure.