Sidebar empty on single post page?

Hello everybody, I’m stuck on a little problem. My site navigations gone when I view a single post of my blog. Suddenly the sidebar is only filled with the search box and nothing else. Is this normal? I checked the single.php in my template and it has the get sidebar code in it. Any help would be greatly appreciated.

Another small problem I have is that my rss2 feed is not working, I get a error page on http://www.mysite.com/?feed=rss2 Do I need to install a plugin for this to work? ?feed=comments-rss2 is also not working.