Help! Server CPU overload

I just received a notice from my hosting company, Siteground, saying:

With this notification we would like to inform you that our in-house Website Performance Monitoring System (WPMS) has signaled that your account constantly uses a large amount of the server’s CPU resources.

As you know, your account is hosted on a shared server and thus sharing the server resources with other customers’ websites.

Your account’s CPU usage is 153 500 script executions per day. The industry standard for CPU usage of a shared account is 12 000.

I have only started testing my wordpress mu site for a little over a week. I have 50 trial members, no one has started their own blog yet.I am using WordPress 3.0.4, Business Portfolio theme. Plugins are: Chat 1.0.2, MarketPress 1.1.6, Membership Premium 1.0.5, Sticky Slider 1.0, Visitor Maps and Who’s Online 1.5.6, WP-CopyProtect 2.1.0.

They want to sell me dedicated hosting at $179.00 to $219.00 per month!

Please, please help and advise.