widgets dissappeared on right hand column
 

The widgets I had on the right hand column have disappeared now. Any ideas on why this may have occured?

You have to give us a few more clues. Did you do anything after which they didn't show up or did you add a plugin after which they didn't show up. What changes did you make. What version of WP and Atahualpa etc.

Normally, when the right sidebar and footer don't show it's caused by the last post or the one that would come after that. But in that case going to a single post should show the sidebar and footer.

In your case it doesn't so I would start looking at the first widget in the right sidebar.
You must have changed something so (as lmilesw said) What did you change?