Well, the problem is that you are running them as one screen. The driver is reporting to Windows that it only has a single screen attached, and Windows behaves as such.
I know in the ATI driver panel there is a setting you can enable that will try and maximize a window onto just one screen, but bezel compensation screws that up.
What you need to do is set a profile, one for Surround with bezel compensation (for gaming) and another profile for just running the two extra screens as extended desktops, thereby eliminating your problem.
do u know how to enable bezel compensation in ati catalyst? i have ATI HD 3870, maybe u can help me..
btw, i don't think eyefinity will work