I'm certain this keyboard has no Break/Pause key. And it is US-layout. I would use an alternative if my keyboard supported it, but it doesn't. For what it's worth, it's an Apple keyboard (http://www.apple.com/keyboard/
), but many other new keyboards lack the button as well-- see the threads in the search results about Dell laptops. Here are just a few I found on Logitech's site:http://www.logitech.com/en-us/keyboards/keyboard/devices/wireless-solar-keyboard-k750-machttp://www.logitech.com/en-us/keyboards/keyboard/devices/tablet-keyboard-android
Since form factors are becoming smaller, keyboard manufacturers are making smaller keyboards as well and shedding some archaic buttons like PrnScrn and Break which have no meaning in modern software. Laptops are doing the same, and I'd bet this is especially true for netbooks.
It should be possible to implement Ctrl+Break with any key combination. Presumably mIRC is just checking the key state at iterations of script execution-- there's no reason it couldn't just check for another key combination at the same time.