I tried mRemoteng portable today. It's great that you are fixing the "old" mRemote and adding new features.
I tried mRemoteng portable on a Windows 2003 Teminal Server, but it says, that RDP is not working.
Before I used mRemote portable on this Server and it worked without any problem.
I also tried t reregister the dll, but that didn't work.
So it looks like there are some differences between mRemote and mRemoteng.
If yo need osme more information to solve this problem, don't hasetate to contact me.