Help!Crash! FatalError"Callback registration failed kMaxCallback"

hello world! anybody know what crashes unity and throws this error? Ive been looking it up online but found very little info, I would like to know what am I doing wrong, is it the actual version? any suggestions?

EDIT: I get the crash three times aday! heard some people are having it since the new update, anyone have some info, a fix.... Im always "ctrl+s" but sometimes forget about it , then the crash happens and lose my info.. :(