aha! so i wasnt the only one! i tried posting a reply to the thread "what would you do" in morals and ethics, typed it all out, came back to find it didnt exist! i was well bemused, at least i know its those pesky gremlins now! think ima have to go gremlin hunting xD
also i think that add-ons can often contribute to these sorts of problems, but also some forum platforms are less stable than others

...for instance i think vbulletin is pretty nice and stable, despite having other problems (mostly usability and admin cp features)
mind you i dont have much experience with mybb....in fact i dont think ive ever heard of it lol, but i have run more than one forum in the past

and it isnt a problem i've heard of before

....ill look into and see if i can find those gremlins, no promises though