Version:            (using KDE 4.3.1)
OS:                Linux
Installed from:    openSUSE RPMs

This is a bug we found internally at VMware, while testing with multiple monitors and KWin from OpenSUSE 11.2.

Host Info: 4 monitor horizontal setup

Open 4 different apps and move each of them to all 4 monitors.
Change monitor topology such that only the first monitor is active.

Result:
You can see the apps that were opened on the non-primary monitors in the task bar but you're unable to access them (i.e. clicking on them does not focus them, unminimize them, etc.). Once you enable the other three monitors again, you can access these apps fine.
This happens with KWin from OpenSUSE 11.2, but not GNOME/Metacity from the same release or even KWin from OpenSUSE 11.1.


Here's one of the windows that was visible on the 4th monitor, but is not visible or able to be interacted with in this situation:

# xwininfo -id 0x2800019

xwininfo: Window id: 0x2800019 "KCalc"

  Absolute upper-left X: 470
  Absolute upper-left Y: 222
  Relative upper-left X: 0
  Relative upper-left Y: 0
  Width: 328
  Height: 275
  Depth: 24
  Visual Class: TrueColor
  Border width: 0
  Class: InputOutput
  Colormap: 0x20 (installed)
  Bit Gravity State: NorthWestGravity
  Window Gravity State: NorthWestGravity
  Backing Store State: NotUseful
  Save Under State: no
  Map State: IsUnMapped
  Override Redirect State: no
  Corners: +470+222 -598+222 -598-553 +470-553
  -geometry 328x275+466+197

# xdpyinfo -ext XINERAMA | tail -5
    red, green, blue masks: 0xff0000, 0xff00, 0xff
    significant bits in color specification: 8 bits

XINERAMA version 1.0 opcode: 129
  head #0: 1600x1200 @ 0,0

Thanks!