Quote - And I have seen it go up to 2.5GB VRAM usage on OS X (haven't tested on XP in a long time). If it bails out earlier, it means that a memory request has been rejected by the OS.

So apparently it is a problem with the Windows version of Poser 6. It's definitely not a problem with my computer(s), Vue 5I (now they've fixed the memory bug) is able to use all my memory without any problem. As I said, I've seen this on Win2000 and on WinXP, on two different computers with different chipsets, so it seems to be a general issue, and not a specific driver/app conflict.
Or, of course it might be I have very, very bad luck, and own the only two computers on which Poser 6 won't work as usual... But somehow I don't think that might be the problem... ;o)

BTW, I imported the whole Poser scene Poser couldn't render into Vue 5 Infinite, and was able to render it in Vue... So there is nothing wrong with that scene either.