Sadly, yes. I still get it as well. Not sure what the deal is. It's been reported to the folks at php (they wrote the program.)
What I did to get around it is to make the club forum(
www.texasmanxclub.com/bboard) my home page. When I get the error (your message posts and pm's work) I just hit the home page. I'm still logged on and just continue from where I was.
I know it's a pain, but this new version of the bboard program is still better (from lots of angles) and WAY more secure than the old program we used.