German Tax Authority Website suggests removal of OpenJDK

[Balans]

Hi,

I live in Germany and use Ubuntu 12.04. The German Tax Authority Website
www.elsteronline.de claims that OpenJDK contains errors (in German:
"...die Benutzung des ElsterOnline-Portals derzeit aufgrund von Fehlern
im OpenJDK nicht möglich") and tells me to remove all OpenJDK software
from my computer and install Suns Java version instead. 

Any idea which "errors" they might be referring to?

Regards,
Sebastian