[Plugin: W3 Total Cache] PHP upgrade question

I’m struggling with a problem and hoping someone can help out. I’m on a vps, and I recently upgraded from php 5.1.x to php 5.2.10. I immediately ran into white screen of death problems. My server admin group helped me determine it was a memory problem with the new php.ini file and changed it from 16 MB to 60 MB. My site is running again, and I switched the php.ini to 64 MB. I’m running the FRUGAL theme which allows for an upgrade to WordPress and allowing it to use up to 64 MB, which is configured. I’m running W3TC, and right now I’m having substantial CPU usage; much larger than I was before the php upgrade. My W3TC configuration is for the following:

Page Cache: disk (enhanced)
Minify: disk
Database Cache: APC
Object cache: APC

Before the upgrade to php 5.2.10, I was getting an average CPU usage of ~0.2 nodes. It’s possible this will settle down, but should I be configured differently?

http://wordpress.org/extend/plugins/w3-total-cache/