[bug] missing texture; material won't show up

so a problem I've run into with Beta5 is that one of the materials (just a simple concrete texture) refuses to show up on my world architecture. instead it gets rendered as a plain white surface. my "world" is made using DTSs (I dont use DIFs for T3d). I haven't had this problem with any of the earlier betas, but in 5, this material simply refuses to show up. if I go in and try to replace it with a new texture manually, then <another> material will disappear instead.

is there a limit to how many materials can be applied to a single model ? I'm modeling my whole city using a single DTS, so I have at least 50+ materials in use on it right now. have I hit some ceiling ?