Media Uploader not working

Hiya

I have migrated my blog to a test subdomain. The transfer appears to have worked as expected. My goal is to play around with a new WordPress theme in a test environment.

After migrating the site, I have tried to upload an image via the stock standard Media uploader. When I do this, the image seems to break in the process. When I follow the link to where the image should be, nothing is found.

Server support thinks it’s a WordPress issue so they have directed me here.

Other things to note:

• Media uploader works fine on the main site under any theme
• Media uploader doesn’t work with any themes on the test site — twenty ten, eleven, etc or purchased
• Have tried deactivating all plugins
• Have tried deleting W3 Cache
• There are no permission errors no are there any errors in the error logs

Thanks in advance for your help!