Very high memory usage on VPS

Hi! I am developing a Web site based in Wordpress which I have access only. The site is hosted in Dreamhost with a VPS.

I’ve been watching my server resources and I have seen that have increased dramatically in a few days. I do not know why this happens because only I have access to the blog based on the latest version of Wordpress (2.6.5) I think it does not have to see the theme used in or the plugins because they all are deactivated. At this time, with all the plugins off the memory used is 140MB memory while the CPU usage is very low. Please help!