Uploaded images currupt on subdomains

Hey

I've got a new subdomain-style install with a problem. Any images I upload to the subdomain sites seem to become corrupted. Uploads work fine on the root site, farmpage.org.

I've tried deactivating all plugins, using the browser uploader, various .htaccess configurations, some wp-config changes recommended on wordpress.org, but no dice.

I also have another subdomain install running on the same box (separate Apache virtual host and IP), but everything is fine on that one. I have tried using the same settings as the working install without any luck.

Here's an example of a png I grabbed from wordpress.org and uploaded.
http://test11.farmpage.org/files/2011/01/wordpress-logo-hoz-rgb.png

This is my .htaccess

RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]

# uploaded files
RewriteRule ^([_0-9a-zA-Z-]+/)?files/(.+) wp-includes/ms-files.php?file=$2 [L]

# add a trailing slash to /wp-admin
RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule  ^([_0-9a-zA-Z-]+/)?(wp-(content|admin|includes).*) $2 [L]
RewriteRule  ^([_0-9a-zA-Z-]+/)?(.*\.php)$ $2 [L]
RewriteRule . index.php [L]

Can someone point me in the right direction? I'm leaning towards blowing everything away and starting from scratch.