Uploading BackGround/Thumbnail HTTP Error

Hey Guys, im new here so i hope this is the right section.

Ehmm, i need some help with my wordpress, see i have try to fix this annyoing problem for days now, and almost giving up hope so i will try if anyone here could help me.
I got a Theme and when i try to upload a Thumbnail or Background image i got this annyoing HTTP Error for some reason.
Could anyone here help me with it?
Im not so pro in wordpress thing so please dont just say change that and all will be okay =)

Here is a pic of it CLICK HERE