Theme issues

How can one change of a theme, knock out my blog? I did change my theme, and then all my right sidebar disepeared? Why? I change the theme back, but still everything, counters, and so on is absolutely gone! I really need help to solw this… Is there any one out there that knows how? I did not get any warning that the Sidebar would disepeared. The blog is back, but not the old sidebar with counters etc.
The Theme is called: The Circling Sky-
Themes for WordPress, Joomla! and Drupal.

Vargas