HELP HELP HELP -- ActionScript 3 Problem

Hi guys, i'm in a trouble, either i'm going really blind or...

I've the following code, in ActionScript3:

trace("FILE: " + soUsers.data.currUser);

currUserID = soUsers.data.currUser;
trace("currUserID: " + currUserID );

currUserID = soUsers.data.currUser as String;
trace("currUserID: " + currUserID );

trace("FILE: " + soUsers.data.currUser);

And i got the following output:

FILE: def1
currUserID: null
currUserID: null
FILE: def1

Can you please, please, point out what i'm doing wrong??

BTW, 'soUsers' is a SharedObject, and 'currUserID' is a string variable;