Interesting titbit I found yesterday after a two-hour troubleshooting session with a customer. One of our application components registers itself in the ROT so that it can be accessed by other application processes. In this particular instance, the ROT registration step fails with the usual cryptic error message "The system cannot find the file specified".
As it turned out, the user had the 'DCOM Server Process Launcher' service disabled.
More details here.
Thanks, Ken, for providing the diagnostics.