I have a good running website. Earlier I used a custom session management and no forum. As I wanted to install vbulletin I installed phplib 7.2c too. I customized vbulletin to work with the phplib session management. Since this update my server is much slower. There aren't many accesses to the forum. My ad-script is phpadsnew which runs on this server too.

Server: Celeron 500, 128mb.

Before I installed phplib and vbulletin the server was running quite good. But now he's swapping all the time.

Does phplib and vbulletin needs so much RAM and CPU?

I'm far from a mySQL expert, but yes, it does require more ram to run scripts like vBull. How much, I'm not sure, but you'd see improvement if you upped server to 256 or 512.