Get yourself as short a DVI cable as possible and give that a try. The static I've been getting has only appeared when I've used DVI extension cables (since the 30" ACD cable is fixed). It got worse when I used a longer extension cable compared to a shorter one. I'm not waiting on a 50cm extension instead to see if that will work. Since I think the Dell 30" panels come with a removable DVI cable, see if you can get a shorter cable. I know its a long shot but its worth a try.
DVI specifications says that a 1920x1200 signal can be sent over cables up to 4.5m in length. 15m for 1280x1024. It doesn't say what length 2560x1600 can be sent over but it stands to reason that it would be shorter than 1920x1200. Maybe the DVI signals sent out by 4870 cards is comparatively weak and so some signal degradation's occuring and giving you this flicker. Like I said, its a long shot though.
