New Install – Presentation Error

Hello ,
I used to have my blog in a subdirectory and have just reinstalled it in the root directory to make life a little easier.
When I log into the admin section of WordPress and click on ‘Presentation’ I get the following error –
Fatal error: Call to a member function on a non-object in /data/virtualdomains/110/hornbag.net/documents/wp-includes/functions.php on line 1345
Does anyone know how to fix this? I’m running a nightly build at present.
Many Thanks and sorry to be a pain I’m just coming across a few issues at the moment.