First, thanks for the prompt replies to you and PB.
Not a lot more to add. Win 98SE; had older versions of mIRC working OK; problem started on new install of 6.O3; have uninstalled and re-installed several times, as mentioned, with exactly same results; I also recall it happening about the same time I got into a brief flame throwing with some guy(?) who called me a "dumbass" in a channel, for asking some tech question quite appropriately; I responded by pointing out how rude he was. This apparently incensed him into a longer diatribe, so I quit mIRC rather than put up with him. That's why I wondered about a possible trojan.
So, when I open mIRC it goes immediately to the main screen and menus, as usual. There is no connection made, or seeming attempt at one. When I click on the Options menu I get a less than 1/2 second flash of the hourglass icon then no perceptible change--nothing, as if I've yet to do anything. I can click and click with the same result. I can use keyboard commands with the same result, etc. There is NO way to open the Options menue, period.