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1. You are missing the language files (English?), or they are not readble by the web server (rights / directory rights), or have selected a default language that isn't actually available or in the wrong location(s). Set to English in Admin until you have it working.
2. Go into Admin/System/Groups Webmasters. Verify that all rights are checked and hit update (even if they look right). Do the same for the other groups making sure you aren't giving too much / too little rights. You should get your rights back.
3. In Admin/System/Prefs/General you can set which module is set for your Start Page (you have none set now). Or set to none and create a custom block in Blocks. Other ways too but these are the easy ways.