Upfront stuck at 15% on loading. Not an internet or network issue

When I attempt to load upfront to edit the site I get stuck at 15% loaded and see a widow that states that another tab is working on the page. I have closed the second computer on which I worked on this site and reset the security keys. Logged off and back on multiple times along with restarting my computer, a mac powerbook. Additionally, once I am on the WPMU DEV site, all actions and page loads are unusually slow. My internet and network connections are fine. Every other site loads quickly.
Please advise ASAP