Upfront Seems "Stuck" at Loading Screen

Team WPMU,

I'm planned up and ready to work and build up these couple of sites. I updated to the current version of Upfront and got ready to dig in. However, when I click "Upfront" to start editing the site, it either says to "wait" in a little pop-up or the "loading" shape icon just keeps spinning and spinning.

This is something that has never happened before, usually it's pretty quick to load. Any ideas what I should do? It's happening on ALL of my sites using upfront (fitscribe.net as well).

Rob