Weird problem - definition of class not found

My folder structure is like this

Root folder
main.fla

Classes
Game.as
MenuScreen.as
GameOverScreen.as
Enemy.as

In my flash file there are movie clips (Enemy, MenuScreen and GameOverScreen)

While clicking Validate Class Definition Enemy and MenuScreen movie clip shows the message ‘the definition of the class was found…’

Only the GameOverScreen movie clips classpath is not found.

I have checked everything (spelling, classpath). Why it does not find the class ?

Is it due to long name or what ? I am stuck. pls help…