iTunes Match album cover problems and double songs

I've got a few problems with iTunes Match. I can't change the covers of songs that already had a cover. When I add a song with a cover to my library, iTunes starts to upload that song. When it's uploaded I can't change the cover, only before it started to upload. When I can change the cover of a song that already have a cover, it's after a few minutes gone and it has the old cover.

The second problem i have is on my iPod Touch. In the album view in the music, a lot of the cover doesn't show up. When i scroll trough my music slowly, it loads the covers. I have a lot of albums so it takes too much time to manually load of the covers.

Another problem on my iPod Touch is that some songs or whole albums are double. When i turn of iTunes Match and delete the songs manually, and then turn on itunes match again it's solved. But after a while other songs show up double again and then i have to do all i said before.

Does anyone know how to fix these problems?

Thank You,

Wessel Bakker