As I re-read my post from a moment ago I want to make a minor correction. From what I know - there are no plans for 32-bit support in the first Vista-supported V5R18 SP??? release. That doesn't necessarily mean it will never happen. Sorry if I implied that.
Apparently Dassault will support Vista for 64bit platforms only, not 32-bit. And it will happen for a "yet-to-be-determined" Service Pack level of V5R18.