I'have trouble with Composer 4 since it's not working in the Admin mode -> Tools -> Episerver composer.
It gives an error the same as this case : http://world.episerver.com/Modules/Forum/Pages/Thread.aspx?id=52192&epslanguage=en but the given link there redirects to Access denied page.
The only differnece is that I didn't migrate from Composer 3.2.6 but directly installed Composer 4.
Can anyone give me some guideline or something helpful ?
Did you read the whole thread? It seems to be related to custom properties which has been moved to a new namespace and/or assembly or deleted, but still exists in the database.