Content dependent on the IP of the viewing user
I think that this depend that you are looking for. See this information if you want to hide a block according certain conditions http://drupal.org/node/134425 (you can custom your php using $_SERVER['REMOTE_ADDR'] to get IP address)

If you want to show or hide whole sidebar, I think that you can make this in template.php (in your theme), adding with php your IP condition, and according the result of condition, set (and/or unset) regions. See this for more/related information http://drupal.org/node/539488