I'm not familliar with the problems you're talking about, but if you could reply and attach a small Maya file along with its exported VRML translation I'd be happy to take a look at it.
You might try exporting as OBJ instead of VRML from Maya and see if the problems you are experiencing change using the OBJ loader instead.
RE lighting, you may prefer to have Vizard apply textures in DECAL mode rather than the default of MODULATE (which applies the lighting models). To switch to DECAL mode, issue:
Code:
myObject = viz.add('theObject.obj')
myObject.appearance(viz.DECAL)