Its not in mojoPortal code its in the runtime, probably ScriptManager.
I'm updating my machine to the latest Mono svn right now, once its complete I will verify if its still a bug in the latest svn, if so I'll email Marek at Novell and bring this to his attention to get it fixed. Its probably an easy fix. If I had more time I'd probably poke around in the Mono source in ScriptManager and related classes and look for where to fix it, but I'm sure they will be able to fix it. Though it may take a while before this is fixed in a release version of Mono.