If you cant send through DCC there are usually a few common reasons why, either your IP is wrong, you're using a firewall wich blocks access to your ports like windowsXP built-in firewall, or any free or personal firewalls like Zonealarm, Tiny, Nortons, and so on. Then you might be using a router that needs to be configured for port-forwarding.
If you could provide some more details (what OS you use, your mirc version, do you use a firewall/router..and if so which Brand/Type) i'm sure we can point you in the right direction
ScoT
#mIRC Undernet