I frequently get that error too, only on this forum. Really annoying as you say because it loses the whole message you have typed in and you have to start again. Also like you I now copy the message before hitting ‘post’ - when I remember 
I just tried sending Niko a one letter message and it worked. I have been using the PM system here for years now and have never seen this error. I normally use Firefox on Linux and do have quite a fast connection although on rare occasions I do use FF on W7 and its not happened on that either. The cookie thing mentioned in Bashy’s post could perhaps play a part but again I have never cleared mine out deliberately and usually my FF profile stays across system rebuilds as I use the same /home directory on Linux and save it on Windows prior to updating.
Stuart
Cookies may play a role.
It is true that I access the forum from several computers, but if thats the problem then it is I would say a bug of the SMF forums because it should not behave this way
I say too fast
because if you repeat (starting with a re fresh of the page) and do each step slowly then the error does not occur
i.e its an auto anti spammer mechanism in the forum I suggest
Not sure that is the case Brian. Often I take 5 minutes composing a reply, hit send and get the error, that is when it is most annoying as you lose a lot of hard crafted text #-o
I can confirm this Brian, it happened to me with very long PMs that I spent several minutes writing
Can’t get much faster than my and Stuart’s single character, no subject, PMs. It’s some kind of glitch but it’s hard to imagine why some of us have never seen it :?
I have had it occur…not recently though
What browser do you guys use?
Chrome
Chrome, opera
I use Chrome too so that appears to be a dead end.
Chrome, on a W10 laptop, Android phone, and CyanogenMod tablet
Chrome here too and on my phone, looks like it could be a factor in this issue…
Well… could be, but dont forget that it is not such a surprise we all use Chrome. It is by far the most used browser, so it could easily be just a coincidence.
I don’t use Chrome but do have Chromium installed here on Linux and will give it a try to see what happens.
Stuart
I just sent a one letter PM to niko to see if it worked OK from Chromium, answer yes … now updating thread from Chromium as well.
Stuart
Hi Stuart, it’s not overly often that it happens, but then when it dies it can be multiple times in a row.
Maybe it’s cause we are using Chrome in multiple machines and the forum add on cookie thinks that we are trying to spam cause it’s coming from multiple machines, I really don’t know, sometimes I have to give up or if it’s really important, use another machine…
When it happens what have you been doing before? I wonder if it could be that more than a certain number of write actions to the forum in a certain amount of time could trigger this as some kind of spam prevention measure? I rarely if ever write a PM after doing any kind of update to the forum.
Stuart