Hi, i got this problem too, after spending a whole night to figure it out, i finally found the solution !
Remove existing referencing libraries (Right click project > properties, remove the libraries under "Android" tab and those in buildpath except for your Android.X.X/
Go to your project, create a folder "libs"
Then place the jars into the folder (andengine.jar and andengineextension.jar etc)
Make them into buildpath by right click on the jars u just placed.
Export ! Wala!