Since chatbox messages seem to get lost/ignored/done incorrectly.
Replace your current smac_cvars.smx by compiling the smac_cvars.sp below. Use this to compile it:
http://www.sourcemod.net/compiler.php Or rather, you can't -_- sourcemod is confused easily it would seem. Instead use the spcomp.exe in your \hidden\addons\sourcemod\scripting folder to compile it.
Another thing you can do is add the following to the end of your smac.cfg found here: \hidden\cfg\sourcemod\smac.cfg
//Fullbright
smac_addcvar mat_fullbright equal ban 0
I met two cheaters yesterday that were clearly using mat_fullbright -_- I'd send you their SteamIDs along with the demo files I recorded, but why bother. All you need to do to remedy the situation is add my suggestions to your SMAC. Good luck CG.