I wouldn't say this is a "sploit".
A problem like this would usually be on the sender's side. Not all IRC clients are capable of supporting resume, or some of them are incompatable with eachother. Try having another mIRC v6.14 user send you a file, and then try resuming it.
Your router/port/bind settings should have no effect on this, as the receiver of the file.
- Raccoon
