LCD stopped switching over to analog signal?

[BoyBlunder]

very weird problem happened tonight. I have a viewsonic VX2025wm (20.1" WS LCD) and I have my xbox 360 hooked up to it via VGA cable (regular video card is hooked up via DVI). well, I got home from work and played for a few hours and took a break. I decided to play later on that night, and fired up the 360. i hit the "2" button on the screen (switches signals) and nothing happens. the screen goes black, and it says Digital on it...when it usually says Analog when I switch over. I checked all the connections and everything seemed normal, but I'm coming up short.

any idea what could be the problem?