Do you see a caching message at the top of the screen?
If you have a lot of content installed, this message may stay there for sometime while content is cached for quicker access later. One way to find out is to open up the Launcher by clicking on it, and picking Developer and then show logs. This will show stuff that's happening that you don't see. If you see a lot of yellow-tagged validating and precaching messages it means that this is going on.
