Just to see if I could replicate the problem, I added
<portal:MobileSkinLink ID="mobileskin" runat="server" RenderAsListItem="false" />
to an Artisteer skin and it immediately broke the page
The reason is because it already exists and there cannot be more than one control with the same ID.
So you do not need to add it to skins generated from our Artisteer plugin because it is already included in layout.master of Artisteer skins. If you want to put it in a different place within layout.master, you can do that but you must move the existing one rather than add a new one.
Note that this link is not part of Mobile Kit Pro it will work with any skin specified as the mobile skin in site settings.
Hope that helps,
Joe