It would definitely have nothing to do with being a featured guild site.
If they're having that problem, have them try to click "Reload" mid-way perhaps. The server is certainly not under any kind of heavy load right now, certainly nothing that should require 5 min pageloads.
If they are having troubles loading your site, are they having the same troubles loading http://www.dkpsystem.com ?
Is this something that's been a regular problem? I don't suppose you happen to know the geographical location of your members who are having this problem?
The reason I ask, is because both of you happen to be EU guilds, which leads me to believe their might be a routing issue from certain parts of Europe to the datacenter in Chicago.