Weird sidebar display problem

I have been having this weird problem recently where my customized right-hand sidebar will display fine for both the home (index) page of the blog, and also on a particular INDIVIDUAL POST, but only when a user is logged in. When I log out to test the site, I see that the customized right sidebar displays OK on the home page, but the content from that right sidebar drops out and moves to the center of the screen. When I log back in again as an administrator or member, this problem does not occur (which can only lead me to the conclusion that maybe it is something with the login page…. I have isolated to test plugins [by de-activating them one by one], and the problem does not appear to be caused by them.

I guess maybe I will try to re-upload the original ‘sidebar’ from my theme, but I would really like to work out a fix if possible.

Thanks anyone so much for your help!