Chosen Sidebar Not Being Applied to Page

Hello folks, I have a few pages on my blog where the wrong sidebar is showing. For example, on this page http://www.arisnelmesidor.org/my-ads-2/, I have chosen the same sidebar option as for the page http://www.arisnelmesidor.org/ads/. On the later page, I have the sidebar I have chosen, but not on the former. Does anyone know what causes this and how to take care of ii? Thanks, Arisnel