I\'ve been working with Eclipse 4.2 (Juno release 20120920-0800) on OS X 10.8.2 for a few weeks now, building apps for Android 3.0 and above. I have a quad core i7 MacBook P
All the above solutions didn't work for me.
In eclipse Under Problems Tab check errors- You might see the unable to delete file and project path name.
Now Go to your workspace directory - Check project.properties for all the project stated under problems tab and check
target=android-21
The target value is valid and exists in your android-sdk/platforms/ folder
In my case target=Google,Google-Api-16 was causing the issue. Replace that and it solved.