Try this:
RewriteEngine On
RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !^
http://(www\.)?domain.com.*$ [NC]
RewriteCond %{HTTP_REFERER} !^
http://(www\.)?domain.com:80.*$ [NC]
RewriteCond %{HTTP_REFERER} !^
http://ip.ip.ip.ip.*$ [NC]
RewriteCond %{HTTP_REFERER} !^
http://ip.ip.ip.ip:80.*$ [NC]
ReWriteRule .*[Jj][Pp][Gg]$|.*[Jj][Pp][Ee][Gg]$|.*[Gg][Ii][Ff]$ - [F]
It is something to do w/ them slashes I'm guessing...
Use the one above as it includes your IP and port 80 and also you won't have to worry about case issues should you get a content provider that names everything in caps and you don't feel like renaming all the pics....