It can't find "API", which sounds like you're using an outdated SMBX version.
But line 33 is weird. It should be calling an error much earlier than that.
This error should occur the first time API.load() is called, and people tend to put their API.load code first before anything else.
EDIT:
http://hastebin.com/lajuhoraba.lua
Ok, yeah...
You may want to download the "Latest" version of LunaLuaSMBX here:
http://wohlsoft.ru/LunaLua/