Yeah earlier today (8am EST till about noon) it was fine. Yesterday I waited as long as 5 MINUTES to get from garage back to main screen.
Now though (about 2pm to3:45pm EST when it happened) - Again took FOREVER to navigate menus in single player. I had to exit game actually. It's a pretty stupid system that requires sever communication to navigate single player menus.
The solution I read in the in-game message was to go into your net connections in the XMB and disable the internet connection, then start game up. Not to just unplug cable....