that error simply means you forgot a ")" right parentesi somewhere in the code. Check the line it says and add it ;P
Not always. Sometimes another error in your code will trick the compiler. It might appear when you have missing or bad data in a Stencyl block, because I think I remember getting similar errors when I was only using Stencyl blocks.
People who use (not just copy/paste, either) AS3 coding (or any other "real" coding language) usually know how to fix this sort of error, because it's fairly common. So I think that the solution depends on what sort of code you have (Stencyl blocks, copy/pasted text code, or your own text code).