Sound check not working on iphone 4 after ios 5 update

After I updated my iPhone 4 to ios 5, the sound check feature of the music.app stops working. When playing music, some songs get a much higher volume than the song before and, if I go to settings > music and turn sound check off and on again it goes to a normal volume.

It was working on 4.3.3 and it works always as expected since my old iphone 3g on ios 3.

I made a change on my settings before update, and disabled the conversion to 128 kpbs on itunes, to make the sync quicker and put much less songs on list to sync. I use the option to sync the songs marked on itunes.

I didn't find anyone on the web with this particular problem a friend of my with an updated iphone 4 didin't noticed anything wrong.