BuddyPress.org

This is a theming issue and more specifically – by the sounds of things – a CSS one, but could simply be that the sidebar is trying to render in an incorrect section of the page.

I’m afraid that you would need to supply a lot more detail than you have in order that someone could help, at the moment it’s a ‘How long is a piece of string’ type question.

Tell us the theme your using and as much detail pertaining to type of install and version numbers and preferably a link to the site so that the issue may be observed.