Some users can't load my site

Wednesday this week I upgraded my site, http://lifering.org, to 3.3.1. Site is hosted on a GoDaddy virtual server. Friday I started getting random complaints that the site shows a “gray screen” or “blank screen” for some users. I can’t reproduce the problem, it loads fine for me in all 4 browsers. For the people who can’t see it, no browser works. We’re getting these errors from people all over the world, and our site traffic is down by 2/3. At this point I’m considering backing off the upgrade. Any suggestions??