It appears that the error is caused by the changes in the PrivacyLevel lookup that was changed in the latest release. Did you upgrade the version of the MonoX without running the DB upgrade scripts? Are other Web parts working?
I just downloaded the newest version and tried to instantiate the Silverlight upoad module (and other parts that are using it, like the wall), and it works without any problems. Could you describe the steps that led to this error?