I noticed that on some of the pics that I've taken, with flash, there is a dark spot on the bottom. It is consistently in the same area, sometimes it's not as large. Initially I thought it was a shadow, but when it started happening in other pics, I thought maybe I messed up the CCD somehow. Here's a sample of what I am talking about. You'll notice the dark blotch, and as Imentioned above, it happens once in awhile.
I took this shot with the kit lens 14-45mm, no lens hood on.