One thing to check for...
If your class is defined as a typedef:
typedef struct myclass { };
Then you try to refer to it as struct myclass anywhere else, you'll get Incomplete Type errors left and right. It's sometimes a mistake to forget the class/struct was typedef'ed. If that's the case, remove "struct" from:
typedef struct mystruct {}...
struct mystruct *myvar = value;
Instead use...
mystruct *myvar = value;
Common mistake.