I get it all the fucking time, I can't navigate. I open up a thread, and it's too busy, I wait a minute and try again, still busy, then at some point it stops being busy, but when I'm making my reply it's too busy, and then I lose the reply.. I started backing up replies in Notepad... I mean, this happens every other link I click. I was trying to read a private message for 1 hour last night.. I didn't exactly sit her trying to all the time, but I tried first and I tried a lot of time in between and about an hour later, I FINALLY got the PM open, but I could not reply, of course.
EDIT: Doesn't appear to be as bad in the morning though (for me - around this hour).