I went looking, and looking, and looking, for a solution to this problem. None of them seemed to fit the bill. I tried...
- updating proguard
- not using libraries I shouldn't be
- re-importing the project
- removing duplicate android jars
- removing all android jars
- a host of other "suggestions" from Eclipse Android users
Not one of the ones I found worked. I suddenly right clicked the project, and happened to see a menu called "Android Tools". I wasn't thinking it would do anything for my predicament, but was curious what was under it. I then saw, and clicked, the item called "Fix Project Properties", and voilà, the error disappeared.
Go figure, an Eclipse option to fix a problem that Eclipse caused. KEWL!
Hope this helps someone through their pain.
IntelliJ folks, PLEASE add GUI support for android, so that I can ditch this piece of junk Java IDE called Eclipse.