I just purchased an ASUS 5770 video card and I'm having some issues with it.
1. If I use the VGA output, when the temperature hits ~70C the picture starts to shiver with small horizontal waves. This phenomena however is absent when the monitor is connected to hdmi or dvi.
2. When playing a game some situations trigger a fan-whistle-like noise which isn't produced by the card's fan. It's mostly audible on static screens with logos or text and changes frequency dynamically as the screens change. Can it be the power supply?
1) I have NO idea. have you tried a different VGA adapter?
2) What kind of power supply do you have? It would be coil whine. Alot of times it is just an annoyance. Just search coil whine if you want to read more. I think there are even videos on youtube so you can hear it. I've had this with past units and even my current one. It only happens at very specific times in certain games.
I experienced the ferrite coil whine issue myself with an HD4890 I bought last year. Luckily, I "whined" about the problem enough for Newegg to replace that card at no cost.
As for the first issue, I too am at a total loss... I'd simply return the card for a replacement. Whether you choose to go through the retailer or the manufacturer is up to you, but I'd start with the retailer first.