Since Windows 8, Microsoft has added another official keyboard layout switching shortcut, Windows + Space. I am Thai who also uses Command + Space on the OS X for keyboard layout switching between US to Thai layout. These two shortcuts conflict on VMware Fusion and the Mac shortcut always win.
Here are steps for producing this behavior:
1. Upgrade the Windows 8 box to Hardware number 9 or 10.
2. Upgrade all VMware tool.
3. Click inside the Windows 8 box.
4. Press Command + Space to switch the keyboard layout.
Expected result:
Keyboard layout on Windows 8 box is switched. (Mac keyboard layout may be switched, this is OK.)
Actual result:
Mac keyboard layout is switched. Windows box shows Metro home screen and no keyboard layout is switched.
Hope you can fix it soon.