Here is a thread that may be useful for you in regards to the dev.exe...
Ctrl, shift, and "." have to be pressed at the same time....I would be surprised if the keyboard was the issue and I'm sorry to say I have no further suggestions on how to bring up the debugging window if this doesn't work...
As for the greater issue at hand...
I have noticed since sometime in diplomacy that the AI seems to "magically" get units at my planets...I'll be playing, and suddenly an enemy ship will appear at an interior world (one that is completely surrounded by planets I've colonized) despite having no notifications of them ever entering my border worlds...
The most memorable time this occured was when an AI had 2 Marzas and several siege frigates that kept harassing me...it would seem like out of nowhere I'd have a marza bombing a planet very close to my HW even though that marza would have had to go through another one of my border worlds to get there (yet I never saw it go through a border world)....
This phenomenon has seemed to happen quite a bit to me and was extremely frustrating...even with psidar technologies (and the like) and no nearby wormholes, enemy units would manage to catch me off guard and somehow be at interior worlds (capital ships and siege frigates were the most common)...it got to the point where I would watch replays just to see if I really was that oblivious, but I have never once been able to see this phenomonen in a recorded game as how I witnessed it in an actual game....as such, I have just always assumed I was mistaken...