I am really anxious to try out this mod in our popular store. However, I just installed the 1.5.0 version into my 1.5.1 test site. All files appear uploaded correctly. However, when I go to the Layout Box controller, there is no "Shopping Cart with Rewards" sidebox.

Could you tell me what would be causing this not to be there?

Again, it's not a matter of enabling it or not. The entry simply isn't there for me to select under the Tools --> Layout Boxes Controller.