Users should be allowed to set the port range that mIRC uses to a port below 1024. What were you thinking when you restricted it to only 1024 and higher? Some people have port restrictions from their ISP and can only have incoming connections on certain ports which may not fall in the 1024+ range.
I'm pretty sure that in previous versions of mIRC, the restrictions forcing it to be port 1024 and higher were not in place. I'm aware how basically ports lower than 1024 should be reserved for certain services and how many systems such as Linux based systems don't even allow regular users to use ports lower than 1024 without access, but I really think you should at least let users set it to a port lower than 1024 if we really want.