Failing to localize WIndows 8 App with Multilingual App Toolkit

I'm trying to localize my Windows 8 App with the Multilingual App Toolkit. And for that I tried to follow this explanation to the point:

http://channel9.msdn.com/posts/Build-Multi-language-apps-using-the-Multilingual-App-Toolkit

but it fails with the following Output:

1>  Multilingual App Toolkit build started.
1>  Merge of Loc PRI file failed calling makepri.exe: '0x80073B08'
1>  Multilingual App Toolkit build completed with errors.

I can't find anything for 0x80073B08. If I remove all xlf language files from the project it compiles, is able to launch and to build a store package. But as soon as there is any language file included it failes to build with the error above.

Any Ideas?

EDIT:

I'm using c# and a single resw file.

Everything works as long as I don't include any xlf files.

There are no duplicate keys (except partly duplicate like "MyButton.Text", "MyButton.[using:Windows.UI.Xaml.Controls]ToolTipService.ToolTip")

EDIT2:

Seems like the real problem is the extension format, e.g.:

ClearNotesButton.[using:Windows.UI.Xaml.Controls]ToolTipService.ToolTip

or

AddPageButton.[using:Windows.UI.Xaml.Automation]AutomationProperties.Name

if I use those makepri throws the exception above. Does this mean I can't set the Tooltip and the Text of a Button via the x:Uid mechanism?

This error code indicates that a (localized) resource add was attempted, but the source resource is not in the PRI file. Three conditions were recently discovered that can cause this condition for resources.

1. A duplicate resource exists in the resjson file.
   JavaScript Example:
   "Cancel" : "Cancel"
   "cancel" : "Cancel" <-- Duplicate resource

2. A resource ID conflicts with a different resource with the same base path information.
   JavaScript Example:
   "About" : "About title"
   "About/OKBtn" : "OK". <-- Resource path is the same as a previous resource's ID

   XAML Example:
   MyButton : "Button without property"
   MyButton.Content : "Hallo Welt" <-- Becomes MyButton/Content, which conflicts with MyButton ID

3. A resource ID contains the same name as the resource file.
   Common Example:
   Filename: Resources.resjson
   "Dialog/Resources/Title" : "Welcome"
   

Please look for these conflicts as they are know to cause this error message. You could also see this error on the preview version. Please ensure that you are running the released version of the toolkit - it is v1.0.1114.0.