I seem to have really confused myself here somehow. Ok, so I created two banners in the Banner Manager:

Positive SSL Seal [in group] BannersAll
Rest Assured with PayPal [in group] BannersAll

I go to LayOut Settings:
Banner Display Groups - Side Box banner_box [blank]
Banner Display Group - Side Box banner_box_all [BannersAll ]

When I go to my home page, the two banners are displayed in the same box on the right, with the title "Sponsors" that doesn't exist! I previously tried creating another separate banner/side-box, "Sponsors", but deleted it when things weren't going correctly.

How do I fix this issue?