I don't know why increasing the 'Texture mem size' makes the game video freeze, as far as I know the dgVoodoo settings only apply to the game once you actually enter a mission - in the 3DFX-accelerated 3D world. The LB2 intro video, though, if that's what you're talking about, is known to be choppy 3/4 the way through on today's computers. This is likely just a Bink video driver incompatibility.

Besides, if you've got 8Gb of video memory, why are you even playing a game from 1997!? You should be running real Longbow simulations for the Army!

You don't need to have more video memory than needed selected in dgVoodoo in LB2 anyhow, as it's probably better to limit what the game has so as to try and slow it down a bit! Don't worry about the video, just set dgVoodoo so the game runs smooth.