Very recent Anti-Aliasing problem

So today I went onto FSX for a bit of a navigation and flight excercise (Runway 21 at Oban airfield in south west Scotland was great though lol)
And basically I found that for reason my anti-aliasing had gone a bit, well, off. I am getting a fair few jaggies as you can see from the image below:

Now I have checked my display settings. 1440x900x32, Trilinear AA (switched on) and all the fun stuff. To sum it up, my settings have not changed since yesterdays flying adventures, but for some reason the graphic quality has and I am wondering what may have caused it.
Nothing has been installed since yesterday
It is affecting all aircraft
My graphics card is an 8600GTS 512mb
Any thoughts? I don't see why it would just suddenly change.
Cheers
And basically I found that for reason my anti-aliasing had gone a bit, well, off. I am getting a fair few jaggies as you can see from the image below:

Now I have checked my display settings. 1440x900x32, Trilinear AA (switched on) and all the fun stuff. To sum it up, my settings have not changed since yesterdays flying adventures, but for some reason the graphic quality has and I am wondering what may have caused it.
Nothing has been installed since yesterday
It is affecting all aircraft
My graphics card is an 8600GTS 512mb
Any thoughts? I don't see why it would just suddenly change.
Cheers