http://bugs.winehq.org/show_bug.cgi?id=20865
--- Comment #26 from Alexey Loukianov mooroon2@mail.ru 2010-06-22 07:08:37 --- I had tested the issue a little bit more and found another interesting thing: if I move any of the Steam windows by pressing Alt+Space on the keyboard and selecting "Move..." from the window system menu then no jumps does happen. Also there are no jumps if I move the windows using window manager keybinding to activate the "mousedrag window move" mode (defaults to pressing Alt on the kerboard and dragging a window with a mouse, but I had it set to use Win key as the toggling modifier).
Looks like the trigger for this bug to happens with Steam is due to Steam uses undecorated windows and tries to manage the window moves itself. Don't know if this proves the discussion related to the causes of the bug or contradicts with them.
Another thing I want to mention again is that now days there are no jumps _while_ moving the Steam window but there's one big jump just after the window had been moved and the left mouse button had been released. And it is typical for window to continue moving following the mouse cursor even some more time _after_ the mouse button had been released (looks like that "left_mouse_button_up" event gets somehow posponed in favour of "mouse_move" events). Sometimes this may last for several seconds if i continue to constantly move the mouse at a not-so-fast but constant speed. It seems that this "never-ending-move" lasts as long as mouse produce a "mouse_move" events being "inside" moved Steam window. Placing some window that takes a lot of resources to redraw under the moved window increases this effect even more: I've been able to get the window continue moving after the left mouse button release for about a minute by moving "Game properties" windows over the maximized main Steam window.
Hope this will help to track the bug down.