I reinstalled my eclipse. and then imported all the projects in the Eclipse, but every project has a common error:
Cannot find the class file for java.lang.Object.
Right click on Project--> Properties, Java Build Path.
Check whether you have JRE installed. If installed click on EDIT and check whether its pointing to correct location
A quicker way will be
Right Click Project---> Properties--->Build Path--->Add External Jars--> Find your android-xx.Jar e.g android-17.jar
In my case I'm using the adt and it is here
E:\adt-bundle-windows-x86_64-20130219\adt-bundle-windows-x86_64-20130219\sdk\platforms\android-17
Hope it helps
I just had this problem and all I had to do was clean the entire workspace, i.e. all projects in the workspace. The error went away.