The server can't hold the huge amount of posts, members, and space used when there's a huge amount of members online at the same time. It's the site's load. Can be fixed by server upgrades, I'm sure. No lag for me recently though. A few days ago it got bad when like tons of people were online at once.
What stinks is almost anytime I've looked to see how many are on line, it usually shows that approximately 2/3 of the people are guests... Like right now... Currently Active Users: 2169 (523 members and 1646 guests)
Why is it happening? Too many people on at once. How is it gonna be fixed? When the servers are upgraded... If you would like to help out with the new servers, there's a place in the shop where you can donate. Those who donate gain access to another forum (Nirvana), and they also get bigger siggie/avatar/profile picture allowances. Clear your history/cache. If you have it set to remember your PW, so you're always logged in, try logging out, then logging back in, too. This should help with that.