If not only MetaTexis is installed on your system, but also other CAT tools, problems can occur. In particular, Wordfast and TRADOS also provide Add-ins for Microsoft Word. If these Add-ins are active, some shortcuts might execute functions of these other CAT tools rather than those of MetaTexis. For this reason, you can de-activate the Wordfast and/or TRADOS Add-ins while you use MetaTexis.
On the first tab: Miscellaneous of the General options dialog box, there is a frame called Other CAT tools.
If any version of Wordfast and/or TRADOS is active, you can un-check the corresponding checkbox to temporarily de-activate the CAT tool.