When changing desktop orientation 90 degrees, clicking apply, and then letting it timeout so the settings go back to normal, most of the screen is black.  I also tried 270 degrees, with the same result.

Hitting ALT+TAB and holding it shows the task switcher, but releasing and hitting tab again does not update the on screen switcher (but will switch to the next application).

The system settings window wasn't possible to find, so I couldn't try fixing it from the gui. To fix it, I unplugged my video cable, and plugged it back in, which I know normally pops up the "a new monitor was connected" dialog, and I thought maybe it would fix it. In this case, that dialog didn't pop up, but it fixed it anyway.

Reproducible: Always

Steps to Reproduce:
1. open "systemsettings"
2. go to hardware/display and monitor/size & orientation
3. change orientation to 90 or 270 degrees
4. hit apply
5. wait until the timer runs out so it switches back
Actual Results:  
The top 85% or so of the screen is black. Windows moved onto it are hidden by the blackness, but they respond to clicks, and make the mouse cursor change when hovering (eg. resize icon, text icon). Alt+F2 doesn't make the command box show up correctly (looked blurry and green like it was just the desktop plus transparency effect rather than the box itself; but my desktop is blue, white and grey cloud stuff, not green). The ALT+TAB display is affected but visible. CTRL+ALT+F1 worked fine, giving me the graphical text mode console (the first one is graphical in openSUSE, and the rest normal). 

Also my virtualbox screen was taking 100% CPU, as seen in top viewed in terminal 1.

Expected Results:  
I should have a normal looking screen like before hitting "Apply"

I am using the "System Load Viewer" widget; I removed that thing with the 3 colored lights that was on the left (no idea what it is), and the defaults for everything else. (clock, tray, notifier, desktop switcher).

I didn't install any special video drivers.

I think my gfx card says "Quadro FX on it", and here is the "hwinfo --gfxcard" output:

38: PCI 400.0: 0300 VGA compatible controller (VGA)             
  [Created at pci.319]
  Unique ID: [snip]
  Parent ID: [snip]
  SysFS ID: /devices/pci0000:00/0000:00:03.0/0000:04:00.0
  SysFS BusID: 0000:04:00.0
  Hardware Class: graphics card
  Model: "nVidia GT200 [GeForce GTX 260]"
  Vendor: pci 0x10de "nVidia Corporation"
  Device: pci 0x05e2 "GT200 [GeForce GTX 260]"
  Revision: 0xa1
  Driver: "nouveau"
  Driver Modules: "drm"
  Memory Range: 0xfa000000-0xfaffffff (rw,non-prefetchable)
  Memory Range: 0xd0000000-0xdfffffff (ro,non-prefetchable)
  Memory Range: 0xf8000000-0xf9ffffff (rw,non-prefetchable)
  I/O Ports: 0xac00-0xac7f (rw)
  Memory Range: 0xfb880000-0xfb8fffff (ro,non-prefetchable,disabled)
  IRQ: 24 (52328 events)
  I/O Ports: 0x3c0-0x3df (rw)
  Module Alias: "pci:v000010DEd000005E2sv00000000sd00000000bc03sc00i00"
  Driver Info #0:
    Driver Status: nvidiafb is not active
    Driver Activation Cmd: "modprobe nvidiafb"
  Driver Info #1:
    Driver Status: nouveau is active
    Driver Activation Cmd: "modprobe nouveau"
  Config Status: cfg=no, avail=yes, need=no, active=unknown
  Attached to: #10 (PCI bridge)

Primary display adapter: #38