Descriptive Problem Summary:
I experienced this problem before when changing or adding images for my profile. The interface is non intuitive and essentially doesn't work.

I go to my settings page and click Browse for the large image, I select my .png off my desktop and I hit Save. The page refreshes and instead of seeing my new image, I still see my old one. Ok.. what gives? Alright, lets try this delete blog check box thing although, I have no idea what that really does. Does it delete the image so I can replace it with my new one? Does it delete my profile image from previously posted blogs? A mouseover should describe what that does if not an explicit '?' link next to it. OK, so trying with the checkbox also results in no change to the image. How in the world do I change my profile image?

I'm going to keep trying and will eventually find the right step but this could be designed a lot better with just few subtle changes.