Long story short - I have accidentally deleted a small area of what would've been vanilla navmesh whilst using the CK and unwittingly saved over it. I now get a 'Skyrim launcher has stopped working' error message when the launcher screen comes up, presumably due to me having done this.

Is there any way of rectifying this??? Help!

I didn't think you could edit the base Skyrim.esm file?
But if you've, by some black magic, managed to do so then reinstalling would be the way to fix it.

neither did I to be honest, but must say I was a tad unsure as to the true extent of what my fiddling around in the CK *had* actually done... cal it blind panic, if you will .

Anyway, It's ok now, it's loading. And thank God for that. It crashed 3 times in a row at the launcher stage and I'd just been messing with the game with the CK immediately prior to that, so I basically thought my Skyrim had pretty much gone to pot.

I noticed this happened for me when I attached a script to the Death Bell... Remove all your scripts from objects (Hopefully that wont be too tedius) and try to launch again.