I just remeber that theres was something like a registry or grouppolicy workaround...
Using the Group Policy Editor I only know the "Turn off Windows+X hotkeys" policy in User Configuration -> Administrative Templates -> Windows Components -> Windows Explorer, but that does only affect the Windowskey + [something] key combinations.
Some things I can think of:
* Does the tool keyview(.exe) from this page
show some input like I get when using CTRL(=STRG in German)+ALT+o?
* What if you change your keyboard layout to "United States (International)" in Control Panel -> Region and Language -> Keyboards and Languages -> Changes Keyboards? Does that have any effect?
* I know this is ugly, but what if you use a tool like WinKey
as a workaround?
* Plug in an other (USB) keyboard, is there any difference?