I guess there’s more Win savvy folks around here and, being late, I’m a bit too tired to fire up W7/Bootcamp’ed for cross-reference. Seems it’s not a Bootcamp issue anyway, if all hardware related sound features run fine and it’s not solely Mac related. Once the Filestream node plays A/V just fine, it should not be a codec/driver issue. Bottom line, it’s a DirectX issue.
Try uninstalling DirectX, Visual C++, .net and codec packs completely, then re-install them. Make sure the Win installations in question aren’t generally screwed.