DCC actually is reversed .. when you send a file to someone,
your mIRC is actually telling their mIRC to connect to your
mIRC to get the file, when someone sends a file to you,
their mIRC is actually telling your mIRC to connect to their
mIRC to get the file. So if you're getting a file, it's actually
an outbound connection for you. So problems connecting are
most likely on the senders end instead of yours
unless your
firewall is blocking outgoing connections.~ Edit ~
Oh, and please read
this post.