I don't think my problem is exactly the same, but it's also an Ogre Exception on startup, so I figured I'll post it here.

As the RWR logo comes up.
This started happening after I was working on my own mod. The only file I had actually changed at the time when I launched was the weapon_specifications.xml.
Other than that, the only other change I can think of is that I made it so the files open with Notepad.exe by default.
Any clue on how to fix this? I've already tried a fresh re-install and I'm still getting the same thing. I noticed the .PAK files open with notepad by default now as well. is there a way I can change that back to see if that's the issue?
Edit: Now it seems to run fine if I install the Running With MP40's Mod, but not if I just leave the vanilla files.
Edit Edit: Figured it out. I had to go into the modded game and change the map to one of the vanilla ones (map1) and then uninstall the mod and run vanilla. Not sure how that carried over from a fresh install.
Anyway, I'll leave this right here in case someone else runs into the same problem.