I am having this exact issue.
Did the following:
You're missing some language strings. Try this. Go into your Admin CP and under the edit languages area, click on 'Write Files'. If that doesn't work, re-upload just the language files from your local
'install/languages' folder. Once they have been uploaded go back into the Languages/Edit Languages are in your Admin CP and click the 'Write Files' choice again. That should fix this issue.
Admin Menu still missing many items.
Any other ideas please???