Can't upload or do anything once logged into server...help!

Ok, so I've been happily writng away on my blog (www.eliboat.com) and I have been having a really irritating problem with FTP. When I try to upload or change any file on the ftp server it just times out and fails to do anything. With uploads I get about 8k into the transfer and then it just poops out. I have enabled my software firewalls to allow ftp access, and this doesn't seem to be the cause anyways because I am having the same problem using my Mac which is not behind any software firewalls. I have a router that has a firewall, but I have set everything to allow FTP on Port 21 with TCP, and my Windows machine is set to be in the DMZ...so theoretically it should not be influenced by the firewall. As an experiment I had my brother log into the server from his machine out in Chicago, and he had no problems uploading a file. Does anyone know what to do here?