Most problems with DCC related to Network Address Translation on routers used by the many who have moved from dialup to ADSL and home networks using router/firewalls. Nothing to do with late versions of mIRC at all.
As for "Software caused connection abort" it is a message that appears when you get disconnected, it is not a source of any problem with mIRC. I have a mIRC robot connected to my channel for weeks at a time (between M$ security updates) and the only time I am affected by "Software caused connection abort" is when there is a legitimate disconnection caused by means other than mIRC itself.
People who constantly get cut off should check other things such as the quality of their phone lines, how healthy Windows is on their machine, the condition of thigns like network cards, wiring, driver software, disc errors, whether the modem is okay or not, etc.
Naturally if Windows is stuffed EG: not updated with current service packs, disc fragmented to the s***house, etc then of course software you install will not perform at it's peak. As a rule I reload all my machines every 6 months. It's not necessary to reload that often but contributes alot towards stability, reliability, etc.
mIRC has one disadvantage for those ready to point the finger in that it requires a continual connection to do it's job, whereas programmes like Internet Explorer and Micro$oft Outlook do not. Therefore it is not always easy to fault-find using software. Nor is it accurate.
