Problem: Every time you upload an image into the Media Manager it creates a duplicate entry and labels it with a suffix of "_01, _02,..." This is handy if you want duplicate versions, but if you don't it can be a pain.
Solution: Delete the image first putting your mouse over the image, then clicking on the little red box with and "X" in it. Once the image is deleted the new uploaded image will replace it. But wait, you say! I uploaded a new version and the old version is still showing! This is a caching issue. Because it is the same name, the browser thinks it is the same file and serves it up from your local browser cache rather than showing you the new version. So first clear the cache then you'll see the new image.
TIP: If you want an easy way to clear the cache, use Firefox and get the Clear Cache button extension: https://addons.mozilla.org/en-US/firefox/addon/1801