ok, so on anything you want to export using NwMax (at least the version I am using) you cannot apply the texture rotation via the material. You have to actually rotate the tverts. The problem with that is the Max4 tvert rotator which is part of the unwrap modifier is screwy and the rotation point is relative to an onscreen value, rather than a flat data value (which is stupid, but I suppose it is based on screen editing, not code editing).
I've put this little bit of code together just now to help you out. It takes all the tverts on a mesh and rotates them counter-clockwise X degrees rotated around a pivot point. UVW values are represented in a 0-1 unit scale, so I suggest rotating all points around pivot of [0.5,0.5,0.0].
Here is a ms file to place in your gmax scripts directory:
https://www.dropbox....md_rotateUVW.ms
open it and execute it to place the two functions into ready position
Then select all the parts you want rotated and run this line in the listener
rotateUVW <your angle> [0.5,0.5,0.0]
Edit: a warning will sound if the model node has any modifiers on it. It should be collapsed first. Reapply any needed trimesh modifier after that
Edit Edit: I also forgot to mention to erase the rotation angle in the material editor, so it will appear correctly both in-game and in gmax for you.
This will also appear on my rollout panel in the next release (v0.91) of my GMAX script library. Look under Funcs Panel > Texture