KevinH, I was going to PM you an epub that might help, but it appears I can't attach a file to a PM, and I don't think it matters what book you use anyway. Also, after thinking about this during the night (when I SHOULD have been asleep, lol), the problem may not be related to regexes at all. I can actually cause this problem to happen just by opening and closing the Preview window, or doing a spellcheck, or opening and closing individual .html files in the epub. It takes quite a bit longer for the slowdown to occur, but if I watch the memory in Task Manager, it climbs steadily. Honestly, if you can't track this down, it's not a problem for me to simply close Sigil and reopen it, especially since most people are not experiencing this problem. I must be special
