The thing that's strange about this is 'Connection Refused' means just that - the server has refused you. Therefore, I can't clearly see why mIRC 6.14 would work and 6.15 wouldn't. I'm guessing an internal change has been made somewhere along the line and now a (possibly popular) external program is having negative effects.
You might want to see this thread
, Norton was suggested. Also try using the Search
feature as a number of threads have been started about this error.
Are you getting this with all networks AND all ports? Have you tried on a fresh install on 6.15?