ActionScript 3.0 :: 1049: Illegal Assignment To A Variable Specified As A Constant

I keep getting this error on the following line:

Code:
dc.score += 3;

dc is an instance of the document class, which contains the score variable. But in the class, I have score declared as a variable, not as a constant.

Code:
public var score:uint = 0;

I remember that the code worked an hour ago, but I don't recall changing anything here.

I also get these:
1195: Attempted access of inaccessible method updateScores through a reference with static type rd2:dclass.
1195: Attempted access of inaccessible method spawnUmbrella through a reference with static type rd2:dclass.