I ran into the same problem, my solution was to install the last Eclipse from their page , (I used Juno, now with Kepler didn 'you have this problem) and the Android ADT plugin. They seem to have broken compatibility with the old version of eclipse in the new ADTs
Naughty, but ... at least it works
You can try the "hard way" by creating the necessary files (build.gradle, gradle wrapper, etc.) manually, but you will have many errors, not worth the time spent.
EDIT: extracted from Android Tools Technical Tools : open the project in Eclipse and export the project from there. NOTE. Make sure you use the latest possible version of Eclipse, as we have fixed export issues recently.
webo80
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