I'm having this same exact problem. I can't get rtecapture.exe to go through the update process and display the main screen with all the options. It just hangs at the update screen. So I can place units but I can't export the mission.
Also, I can get RTE running single player and I can see options to start a new editor in the multiplayer mission list but I can't get RTE to start in multiplayer. When I start the editor from the multiplayer mission list screen ("Create Game" screen), preview it then hit ESC I do not get the same black RTE menu that I do when I use the editor in singleplayer mode. Does anybody know how to remedy this?