Long load times for big categories

[cedivad]

Hi there. I read the annuncement, and I hope the category is right, else do what you want
The website url is http://it.tnntp.com/
It's a edited version of the vbulletin's archive, posts come from usenet.
The problem is that when i show a big category (like this) it takes long time to load. Threads (like this) loads istantaneally; server is a dedicated "not too old one", Pentium 4 3Gh, 2GB ram.

Can i do something to decrase the long load times?

Thanks!