OK so this has finally done my head enough to ask others if they have any idea what the issue may be.
Everytime I press the apostrophe key (or SHIFT + apostrophe to get an @ symbol) on my keyboard it takes around 2 seconds to actually print the character on screen (at which point a whole array of @@@@ symbols or apostrophes pop out unless I am quick enough to time it right and just get one). It's Almost like a sticky key, except sticky keys are turned off. Toggle keys are off as are filter keys.
Everything was fine until one random day it happened, I haven't changed any settings in Ease of Access center.
I have a Logitech G15 - Drivers all up to date, on Win 7.
One other interesting point is that when using RDP the key works just fine on the remote machine!
Has anybody ever encountered anything like this before?
I changed my keyboard input language to US and now my @ symbol works in Chrome, Visual Studio. But not in notepad, when pressing SHIFT + ' (apostrophe) key in notepad I get a: " (quote). I'm now all sorts of confused!