Custom Header shows as blank

Hi, when I upload a header image it shows as a blank white image, I think the same problem also means I am unable to upload new images into pages too.

The source of this issue is undoubtedly recently switching from one domain to another (now http://www.yorkontherun.com used to be http://www.sitejogging.org). I managed to restore all the previous content and links to my previous images but cannot upload new ones.

Please help me with this, UK2 (the web hosting service) have abandoned me now and recommended asking on the forums.

Thanks a million for any help, I really desperately need it.