EDIT: This problem has not already been resolved in the other suggested SO question
I had a fully working app on the market for over a year, with ve
May be its a Build Path Configuration problem.I did the following to solve the issue.
1.Right click on your project and go to Java Build Path.
2.Click on Order and Export tab.
3.Check Android Private Libraries and other 3rd part libraries if you have added.
4.Press ok and clean the project. I hope it will solve the issue.