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
just right click on eclipse and run it as a administrator i was also having the same problem after this it was working fine actully sometimes the windows do not give the permission to access to sdk in normal user so you have to give admin permissions in order to work android sdk or content loader
this approach:
shut down eclipse then go to YourWorkSpace\.metadata\.plugins\org.eclipse.e4.workbench and remove "workbench.xmi", now restart eclipse.