Problems with permission at host

Hi,
First i had my blog at godaddy but in my opinion it was slow so i searched for another host. Now i use mediatemple as host, read a lot of good things about them. But when i install WordPress i got a problem with my permissions. I can’t upload photos, can’t use the edit function in presentation.
At godaddy i didn’t have a problem with all of that and even the permissions where the same.
Is it the htaccess or someting else? I just can’t figure it out how to get it to work…. already contacted mediatemple support but they said that there is no problem with the permissions.
Does someone have, or had the same problem?
Hope someone can help me.
Thanks