yeah, it's odd, it tends to just be these two friends who I jointly email all the time. No they have nothing in common email address wise, one has a gmail, one has a work address. It does happen sporadically with other people, but it's mostly the two friends.
Can't remember the exact wording of the error message, is along the lines i wrote above - you get hte option to try again, save to drafts or keep writing, so i choose keep writing and then go back, copy what i typed, exit out of safari, go back in, re-enter it and then it sends. Sounds convoluted but it's quick enough. it's just very irritating that it happens so often.
I changed to firefox there and just sent them an email with no problem. Could be the answer.