also. if you are using win7 or vista, you may in some cases benifit from doing a scandisk on the drive with EC. they both (in some cases) got a bad data corruption issue, not caught by the patcher.
Computer - Right click drive in question - properties - tools - disk scan (tick automaticly correct error, but leave scan sectors uncheckeed).
disck scan without sector scan typically take 2-10 min depending on disksize and number of files on your disk, note that your pc will schedule a scan for next time your pc is restarted if its the system drive to be scanned.
would like to point out its an issue in windows, not in EC
Actially it's Properties->Tools->Error-checking in Windows 7. It requires a reboot to run as it will not check the disk while it is in use. There is only a very slim chance that this could be the problem, but it never hurts to check.
From my experience it's a graphics timing issue. I've not done any scientific checks so don't know about memory leaks and such, but when I have experienced it I was generally moving rapidly through a graphics intensive area. Lots of trees, or things like that with a myriad of small graphics units. I'm runing a 64bit HP laptop with DirectX 11. I've not seen a lot of dropouts, but always at a most inappropriate time.
The DirectX issue is twofold. First, DirectX 11 (and 10) are supersets of DirectX 9 and below. As such they have all the functionality found in earlier versions. However, not all the DirectX 9 libraries are installed because their functionality is redundant. However, programmers don't always plan properly, and when they programmed for DirectX 9 their code looks for DirectX 9, not 10 or 11. This would go back to the core system that is driving all games based on a particular engine. When the program can't find the library it is looking for, it doesn't know to look for a newer library, so the inevitable result is an eventual crash.
If you go to Microsoft.com and search for DirectX End-User Runtime Web Installer you'll find the link to download the installer. This will install the optional components that should fix, or at least minimize the problem. Of course, no guarantees.
From a programmers point of view, the fix is easy. Instead of looking for 9, look for 9 or greater. (>= in programmereze). Unfortunately, when the game engine was written, 9 was the latest and greatest, and nobody expected there would be a 10 or 11. By the same token, when Microsoft created 10 and 11, they made it backward compatible to 9 and below, so why include the old libraries? The old Catch-22. Fortunately the fix is still easy, but just takes a little time to download and install. However, it is pretty seamless.
Kind of a simplistic explanation, but hope it helps.