title: Android: Eclipse can't build projects
body: <p>days ago I opened ADT and it suggested to update 2-3 things. I did without even looking what they were, and after it all gen folders are empty. I have about 40 little projects, and they all don't have  R and BuildConfig classes. I can't create a new project, "Compile With: " field stays empty. When I open "Android -> Properties -> Android" then everything is empty there, no Project Build Target and n o Library, and no possibility to add.
  I cleaned many times, Built manually and automatically, insatlled Build Tools in SDK Manager. no error in any layout file. what else to do? Help please.</p>