ok, this is defiantely mirc fault.
i have 2 6.16 running and i just executed on first mirc /whois command on myself and i got this [10053] Software caused connection abort, so i look on other mirc what error it is (so i can compare) coz i have them in same channels, but look at miracle, mirc (2) didnt even showed mirc(1) quit...

so i guessed mirc(2) is also f*cked up now...
i do the same //whois $me on mirc(2) and woila
[10053] Software caused connection abort

yep, i beg khaled you to fix this on 6.18
it become too much annoying