The connection itself is no issue, it's getting a pleo identified as such to software (Dinomite, if I recall correctly?) which looks for a pleo connected by USB. A different issue is the upgrade software not working with 64-bit windows, but that has nothing to do with the USB connection either.
So no, there's no 64-bit Windows driver for pleo, but I don't know if that's really an issue if you're just after the connection itself? I know nothing about USB access on Windows, but I do know that on Mac OS X pleo can actually be connected to using terminal software and sent commands, all without installing any driver at all. And OS X doesn't know anything about pleos out of the box, so the same thing shouldn't be impossible on Windows.
But then, what do I know about Windows
...
(And sorry if this got a bit rambling and unstructured, it's Monday night.)