Phone not jailbroken...

I have found out what it is. I am installing an app that is 1.6gb, and it is a failed effort at getting it on. When I managed a full install it went away. The problem was that even though I had 3.2gb free, it kept saying I didn't have enough space to install the 1.6gb app... WTF! So needed to clear that lump of data so it would install.