OK, I think I know how this works now. It's the size of the commit to the database and I'm locked out by the hosting service. So I guess I have to stop posting articles (or break them into smaller pieces)
People tend to look at you a little strangely when they know you stuff voodoo dolls full of Ex-Lax.
Hi! I've transferred to the new host (and had to update phpBB to do so)--as you can tell by the funny-looking default theme lol. Luckily I was able to rescue and upgrade the database, but for some reason only up to a week or so ago (whenever it was I responded to your Happy New Year). I don't think there were too many posts after that.
I don't know whether phpBB 3x acts differently than 2x in terms of post length or characters, but hopefully this solves some posting problems or at least doesn't cause any more.