After a level is completed and the screen camera drops quickly down the pipe, I can see a line where the "blackness" does not reach the top of the screen and the last level can be seen behind it.  It looks around 4-6 pixels high.

When that scene finishes, I think I can see the same thing happening on the left side of the screen, but it is a lot quicker and I can't be sure.

For the record, I am on a wide screen laptop running at 1280x800 at default, and WOG is in full screen mode (not expanded window).

<edit>
After a few more runs and some very poor attempts at getting a screenshot, it looks like the texture that is doing the "fade to black" effect is offset from the edge of the screen.  It also seems it isnt the last level showing up, but just the movie itself

<edit 2>
Several more screenshot attempts.  I am fairly certain now the issue is not being captured within the screenshot, yet I am also certain I am seeing this issue...