Mysql loading very slow

I’m running a forum system on my server. Loading pages that don’t connect to the forum database load normal. Whenever I browse any page that connects to the forum database on my forum, the page either takes ages to load or times out loading. I never exceed using 14% of one of my two cores, I’m using a quarter of my 1.5GB ram. It’s only been loading slow like this since I’ve switched from running Windows to Ubuntu Server 8.10. I enabled logging slow queries on SQL, but nothing’s been recorded. I’ve installed the server packages through Webmin, if that’s of any help.
Also, when I access the server through its local IP address it’s still very slow.