If just pressing the console key deactivates achievements then this is totally [censored]. Many European keyboards have the Tilde console key mapped directly to a key that's to the left of the number 1 key. It's also just below the ESC key and just above the TAB key. This means it's extremely easy to mistakenly hit that key during combat when switching weapons or when accessing the Options menu with ESC.
I've tried editing the bAllowConsole=1 entry in the Fallout preferences file and changing it to 0 but this does nothing. I assume this is disabled and the console value is hard-coded?
Also, why do I get 0 results when I do a forum search using achievements? And why are obvious questions like this not in the FAQ?