Well I was able to fix it, but I still don´t know, what
went wrong there.
1.: give _progressSWF a name of "_progressSWF" before it is
added as a child (line:465).
2.: give _percentLoadedLabel a name of "_percentLoadedLabel"
before it is added as a child (line:475).
3.:Get them both by the name (line:487 appr.).:
The errors disappear, with me not knowing why (and I
don´t care for the moment.