try doing your lighmapping in tool. if you don't how heres a link. i had a similar problem that you have. but doin the lightmapping in tool is much easier and i find it faster. http://www.halomods.com/forums/viewtopi ... highlight=
goto the link that i gave you and try running lightmaping in tool. if it doesn't work then you will probably have to rebuild your scenario file and then try the lightmapping again. (thats what i had to do before anyway)
actually it does have to do with the lighting because if you ever opened your scenario in sapien before running radiosity you don't see anything of your bsp. once you run radiosity/lightmapping then your level shows up. in your case you stopped the radiosity too early and so you only see half of your level. so i would suggest once again to try redoing the lightmapping.
There is a problem with the way you UVW mapped your BSP model in 3dsmax (or Gmax). Re-apply your bitmaps, apply a UVW Map Modifier BUT DO NOT apply an Unwrap UVW Modifier... you dont need that... just do what I said and if the textures show up the same way... than you either moved vertices or faces which messed up the texture coordinates... thus giving you the fuxxored bitmap appearance...