This may be an issue in other browsers too.

When the super references are set, a name parameter is set on the function reference on line 192. This allows the name of the anonymous function to be retrieved from the caller when calling the super parent.

this[i].name = extendee[i].name = i;

It appears name is reserved or overwritten in Firefox 4.0.1 and possibly other browsers.

To fix this change name to another variable name on line 192 eg

this[i].fName = extendee[i].fName = i;

Then change where it is retrieved from the caller on line 164 eg

var caller = this.sup.caller.fName;