Hi there, hmmm ok it could be then that there’s some js conflict which is affecting the admin area. If you go into the theme folder via FTP, click on the style.css inside each theme and view it, and at the top you’ll see the version number.
Here’s a screenshot with another theme I had open to give you an idea – http://screencast.com/t/oLJSrGEhfLUF
The latest version of the theme is 5.5, so delete any earlier versions leaving only 5.5 active. It doesn’t matter if you remove a version which is currently active, as WordPress will revert to the default theme, then you can just go back in via appearances>themes and select the theme you wish to be active and save.