Delayed Cycle Through Multi-Site

We installed W3 Total Cache but had no improvement with our problem. Every time we click something or take an action, or even just log in, we have to sit and cycle through every blogsite first. We tried using Firebug and couldn't find anything. Cookies enabled. Attached image shows what we see. We have a VPS with 7 nodes and 1.5 gigs of RAM. Fewer than 10 users at the moment, no traffic. We need to ramp up to several hundred domains quickly but can't do so until we solve this one. Thanks very much!