Newbie having trouble with Sidebar in this Theme

I seem to be having some trouble with the theme I have chosen for my site. On the Archive page only, the comment text seems to be breaking the sidebar image apart. Refreshing the screen brings it back but as you scroll up and down the image breaks up. Now I have only had this happen with this theme, but not on other ones. However, due to the nature of my blog, I am really counting on using this theme.
Note: it is only on the Archive page