try this site: http://support.microsoft.com/default.aspx?scid=KB;en-us;q227148

also, be sure in your LAN , on the gatekeeper, you have forwarded a range of ports for mIRC to use, then put those ports in mIRC's options, under file/options/dcc/options where you see the default of 1024-5000

ParaBrat @#mIRCAide DALnet