I think the reason for this is because we have the ALT-SHIFT shortcut to place the User Origin to a new node closest to our mouse cursor.
In Windows, this same ALT-SHIFT shortcut is the default for switching between keyboard layouts.
Under Windows 7, I can show you where to turn it off (also see attached image):
1. In Control Panels, go to the Region and Language Control Panel. In that Dialog, go to the Keyboards and Language tab page.
2. Click the Change Keyboards button.
3. In the new Dialog, switch to the Advanced Key Settings tab page.
4. Click the Change Key Sequence button at the bottom.
5. In the appearing Dialog, switch both settings to the Not Assigned radio buttons. Then click OK.
After this these settings of the system should not get mixed up with ArchiCAD shortcuts.
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