Latest Upgrade from 2.7.1 Failed – Need Urgent Help

Hi,

I think my other post failed so i’m making a backup.

Basically i tried upgrading from 2.7.1, refreshed the page and there was a white screen with the message saying under maintainance.
I deleted the maintainance file from the web server, refreshed the page again and now theres a fatal error whenever accessing the front or backend;

Fatal error: Class ‘WP_Widget’ not found in E:\domains\l\londonbicyclevaletparking.co.uk\user\htdocs\wp-includes\default-widgets.php on line 15

My website is http://www.londonbicyclevaletparking.co.uk

Thanks in advance

Naweed