Here is the code: src[equal]http://img.zerosecurity.org/files/=src[equal]../../uploads/
I also notice you have some subdomains (ext.zerosecurity.org or img.zerosecurity.org) Please note when Timthumb host (subdomain+domain) was different with source image it may be assumed as an external image. You need to enable external images in your Timthumb configs (edit timtumb file) to make it work. Ignore this if relative URLs works for you.
As I said I think it’s a problem with your PHP or Apache configurations.
Your server doesn’t allow us to use relative URLs. HMWP config is correct so you need to ask your host company support for more help.