For those of you getting the error message "An error message cannot be displayed because an optional resource assembly containing it cannot be found":
You get this message because an debug assembly from Microsoft is not installed by default on most devices. The actual error that happened is unrelated to this, but the system could not display the error message because of the missing assembly.
For WM6, we have posted the install here. The CAB comes from Microsoft and is a part of their standard .NET Compact Framework installation on the desktop.
http://www.beejive.com/wm6/lib/System_SR_ENU_wm.cab