When you try to open the Distributed Application Designer from a console installed on an x64 server you may see the console crashes with .NET error in the Application Log (something of type badimageformat).
This seems to be a bug in SP1 RC. To work around it use a console from an x86-32 (32 bit) machine to connect to the x64 server.
On OpsMgr 2007 RTM this issue does not exist.
OpsMgr, Operations Manager, Application, Software, Microsoft
Source:? Technet Blog