About 3 months ago I got myself a brand new PC with a 24" Full HD monitor. The 1920x1080 pixels are awesome. Watching Full HD movies and playing games in Full HD rocks.
The monitor came with a VGA cable but also has a HDMI input. I was thinking about buying a HDMI cable but decided to save 10bucks and left it running on VGA.
One thing tho was making me angry, it would flicker in games. No matter what game or settings. I thought it's something with my configuration and barred with it. But recently I saw some computers in our office with Full HD monitors flickering in some cases, also with a VGA cable. So I went to the store and got that white HDMI cable (my monitor is white), plugged the monitor, started Star Craft II and.. No More Flicker!
I did try to google for a reason but got no logic answer so I just accepted the fact that HDMI is worth it. My best guess is VGA can't deliver the huge amount of data to the monitor so it skips frames and so the flickering is produced.
Get yourself a HDMI cable today (or at least a DVI)!