In my case, I'm using my own library (MyLib) shared between 2 apps. App A was closed when I added a new class to the library.
When I opened App A to work on it, Eclipse recognised the new class, and I was able to reference it. However on running I got the error.
It turned out that the imported library folder in App A (named something like MyLib_src) didn't reflect the changes made to my library project (MyLib).
- To solve this I refreshed App A, the changes reflected, and Android could build my project correctly.
I have found no reference to this version of the problem, so thought I would add it to this list.
