Version:           KDE 4.3 Beta1 (using KDE 4.2.4)
OS:                Linux
Installed from:    Ubuntu Packages

I use the standard settings for the window's maximize button: left click resizes horizontally & vertically, middle click resizes vertically, right click resizes horizontally.

When I just use the left mouse button it does work as expected, window gets maximized and restored to original size. Now I maximize the window mit left click, then I use the middle mouse button to shrink the maximized window just vertically. Then I maximize the window again either with left or middle click. Everything's fine so far. Now I want to restore the original size from that full maximized window. So I click the maximize button with the left, which is defined as both direction resizing. But instead of restoring the default size the window gets only shrinked vertically as before. I need to then click right to restore the original size.

This means once I have used any other mouse button than the left one on the maximize button I cannot restore the maximized window to default size with the left mouse button but always have to use either left + right click (as described above) or left + middle click when I used the right key to downsize the window from full maximize. The original window size is remembered but not used, instead the last used window size is restored with a left click.