FTP sites and Apache as a proxy server

[TSMJ]

Hi
I've just been fiddling with apache and have set it up as a caching proxy server. I don't know whether its how i've set up the browsers on the client machines, but I cannot access FTP sites (using IE or a FTP program). Can somebody tell me how I can get FTP requests to go straight out rather than Apache intercepting them and getting confused?

Thanks