Combination of factors... over 1000 users logged in at any one time, and a ton of java-scripts running, both as ads and forum features. I complained before when some of those features were disabled, but now I can see that they actually do pose a problem when too many people are accessing them at the same time.

I've had to resort to java-blockers to get it to actually work... it's still slow compared to other sites, but it's bearable. The Java-blockers still allow most of the ads, but somehow, excluding Javascripts enables tsikot to load faster.