With the way that the sidebar is underneath the content it seems that your html/css formatting got messed up. This also could be why your footer disappeared. Did you change anything beside adding content? Did you change the css/html/php?
Try looking at your formatting...or what have you changed. Could be something as simple as you having a post that is too wide (like a really long URL)
EDIT: I quick played around on firebug on you need to float your footer left:
float:left (get rid of your position:relative)
I don't know how you had your sidebar before but this is defiently a float/position problem.
EDIT2: Your sidebar is located underneath your "content-left" div tag - your sidebar should be on the same level as your content left:
<div.....><div id="content-left".....>....</div>
<div id="content-right".....>....</div></div> you have the content-right nested underneath the left
Therefore you can fix this by floating your footer and then fixing your tags to allow for your sidebar to float to the right and your content to the left.