I have KDE up and running on two monitors connected to one Radeon 9800. The setup is such that one X server is running two screens, so the mouse moves freely between screens, but you cannot drag windows between the desktops. In other words I am not using ATI's "big desktop" mode (similar to nvidia's "twinview"). This is all well and good, except for a few little bugs here and there.
Some window elements that should be rendered on the secondary screen are instead shown on the primary. For example, in KDE, you can configure things such that when you launch a program, a smaller version of that program's icon appears next to your cursor while the program loads. This little icon is rendered correctly if I am launching something on the primary desktop, however when launching an app on the secondary, the icon is rendered to both monitors. It follows the cursor on the second monitor, and matches movements on the first monitor. The cursor is NOT duplicated. Only the little "loading" icon.
Another example is the very top of a KDE window. KDE renders its windows with rounded corners. The very top edge (~3 pixels) of this rounded border is rendered on the first monitor and NOT the second monitor. This results in a weird little transparent area with a 1 pixel border attached to the top of all windows on the secondary monitor. Also, since this element is rendered to the first monitor, it obstructs whatever your doing.
Random other elements (scroll bars and such) are occasionally rendered to the first monitor as well. Note that the converse of all this is not true. Elements intended for the first monitor are never rendered to the second monitor
I'm sure some of my descriptions are a bit tough to follow, so here are some screenshots:
Screenshot 1 shows what happens when I move a window on the second (not shown) desktop. As soon as I refresh the desktop, all that blue junk disappears. In screenshot 2 you can see the little gimp icon being generated as the gimp loads on the second screen.
So, any guesses how to fix this?