Wow, this is the first time i've heard of anything like this happening to a new-ish flatscreen monitor... It was very common on old CRT's (that's why they invented screensavers in the first place).

Your best bet is probably to call up Dell support and ask them what is going on. You could also have a look through the manual for your screen, see if it says anything about running for prolonged periods of time at a non-native resolution.

What? (At the bolded parts)

Lets debunk the nasty rumor that games kills hardware. If there's a problem with said hardware, it'll manifest it self sooner or later in any event, regardless of any games it may be exposed to.

Secondly, such a large screen, and widescreen no less, must have a native resolution of around 1680 x 1050 or so. Why would you run it at anything less then that then? Especially 1024x768, it must look like rubbish!

Now, to your problem. It sounds like some form of image persistence, though it's rarely seen on modern LCDs. It happens because the monitor is displaying a static image, that doesn't change. Sins would be anything but static in my book, unless you just left the game sit there for 10 hours without any interaction.

If it really does have some form of image persistence I'd suggest you turn off the monitor for an extended period and see if it sorts it out. Otherwise you may be able to use a program try and fix the screen.

You could try something like http://www.jscreenfix.com/basic.php I guess, though it was the first thing that just came up on google, so there may be other/better/different tools for clearing up the persistence.

In closing though, run your LCD at the native rez and refresh rate, and not anything else.

If he is heres his fix

Buy a new monitor.

I'm talking about an LCD flat panel monitor, not a CRT.

Well, good news. After leaving the computer off for about 10 hours, the smudges have gone away, so it seems not to be permanent damage, at least so far. We'll see after more long sessions of SINS. I do think this is worth commenting on, because I've never had any other program leave persistent images on this monitor.

It took me awhile to track it down, but the monitor is model number Dell 2005FPW, which I see is a 20W, not a 21W as I said above. According to the manual, it supports frequencies up to 75 Hz (except only for the supposedly optimal setting of 1680 x 1050, which must run at 60 Hz, and which I don't like as much as good old 1024 x 768). So at least it seems I haven't been running it wrong for two years.