Sorry to hear you are having problems MELFRITSCH115.
We have a thread to report such errors here:
Error Report Thread
I can not say that I have seen or experienced your error, however please try some of the solutions in this thread:
RealPlayer Troubleshooting Guide (Solutions & Tips)
Most specifically, ensure you are using Firefox and RealPlayer version 10.5. If none of these solutions work for you, please post in the Error Thread and hopefully we can get you working again.