I'm having a hard time tracking the cause down without Win98 (It works ok on Win2000 & XP).
As a stopgap, just assign a blank white texture (a 256x256 white block will do) as the lightmap, and it should behave as if there is no lightmap at all.
As a stopgap, just assign a blank white texture (a 256x256 white block will do) as the lightmap, and it should behave as if there is no lightmap at all.