Well, just to try it, I'll tell you, if it improves it, I wouldn't advise you keep it off, because I'm not exactly sure what effects it'd have (nothing deadly, but its possibel more scripts could be ran on your machine if not protected right)
Go to the Control Panel, and go to the System Tab, then to the Advanced tab.
Now, select the Settings button under Performance, and when in that, go to the Data Execution Tab, and now select the second option to keep it on, and click Add.
Find Internet Explorer (.exe) and make it appear on that list, and also with MSN Messenger (.exe), and then if that works, try one at a time.
What this will do is cancel Data Execution Prevention on these programs until you choose to allow it.
If one of these fixes it, we might be able to narrow down the problem, and if it is Internet Explorer causing it. You could try another browser to see if the results are the same or not (I know I said I wouldn't do that
I hope this helps.