Forums mIRC Help Common topic but so far nothing worked

There are so many with the same problem: able to connect, but 99% of the time sending DCC file to others fail.
I know that some people's setting block some file type but jpg or wmv is too common to be rejected.
Is it possible that the port settings in my computer may be interfering? I use a firewall (match ports with mIRC) or Router (opened ports to allow mIRC). Using Passive DCCs.
What else could I try?
Using broadband, Vista Home Premium.

Passive DCC reverses the DCC connection process and requires the receiver to have a correct network setup. Turn DCC Passive off, confirm your firewall/router settings and try again.