If you're not quite sure why error message shows up, just read it carefuly. What is interesting for you, is this part.
Index already enabled : main : bool start() : 146, 2
Now what that mess means.
Index already enabled
You've used SetSendParameter() function twice on same parameter, and engine doesn't allow that; you should recheck the place where error takes place...
main : bool start() : 146, 2
...and you can find it using this part. First is module (main), then function(bool start()), and finally position in
preprocessed file. Open
main.fosp file, which is the one and jump to line 146 - that's where you made something wrong. File is bit harder to read, as all defines/macros are already translated, but when you compare .fos and .fosp files, mistakes causing engine to cry are easier to find, and maybe even fix.