Alt shortcuts not working for alt-left/right or for é, í etc

Hi guys,

I've had this problem for a while now… Essentially, the issue lies in the alt-shortcuts for left and right where one is usualy able to 'word jump', and the creation of accented characters like é and í using the alt-e shortcut. All other alt functions appear to work fine for the moment. The alt-left/right shortcut still works when shift is held down, and highlights all the characters that have been passed over, as it should. The output for alt-e is completely blank, and the alt-left/right output is nothing, unless shift is also held.

I have a British English MacBook Air keyboard on Mountain Lion, and I have set it to that layout, and I regularly switch between this and greek for scientific formulæ. I've fiddled around with language and input settings trying to get it to work again to no avail, and there are no shortcuts programmed to that to my knowledge. I have checked on a guest account and it seems to be account specific. Ideally I'd like to keep this account without migrating everything over - does anyone have any ideas with regards to how to track down where the problem is?

Thanks in advance to any responses!