I am on Windows 98SE mIRC v6.16. I'm pretty sure it has nothing to do with the operating system since the problem is only evident in mIRC.
How are you so sure? The bug is unable to be reproduced by 2 people on XP, both sp1 and sp2, and yet you seem to have the problem on 98se. The operating system cannot really be ruled out until more data is collected. Also keep in mind, just because it only happens in mIRC, does not mean it is necessarily mIRC's fault (RE: dns bug, various other mIRC glitches due to windows bugs, etc)
I am a programmer and in my field of buissness, windows glitches are no excuse for making unstable software.
Anyway, I use several programs that make all kinds of connections on this system (servers of various kinds, p2p that maintains long-term connections, etc; I have several Win98SE boxes) and mIRC is the only program that ever crashes in this way (at it is only maintaining two or three connections). I call this a mIRC bug even if it's some unhandled exception in the OS, it obviously can be handled as it is in all the other programs and so this is a perfecly valid bug report. Just... fix it.
I understand the bug is hard to reproduce. Because of it's predictable nature (only crashes after reconnect) I can gather additional informations using debugging tools, just tell me how.