LAMP, PhpBB, performance issues after initial optimization

Using Linod 512. Last night I followed the Linode guide for setting up LAMP on Ubuntu 10.04, connected it to my Domain Name, and then set up PhpBB on the site. Seemed to be running fine last night. Then this morning I checked things out and even SSHing or LASHing into the server took forever, and I was lucky if I could load the site.

Then, I followed the guide for memory and networking, altered the mysql config and the apache one, reset apache, and it seems about the same. My largest process is Mysql: 3.8% Mem 0% CPU. Not sure what else I can do or what is wrong. I will admit I do not have a strong understanding of Apache. Any pointers would be great. Thank you!