Admin screen suddenly looks weird

I installed a clean version of WordPress on my server a couple of months ago and everything was working fine.

However I logged in again today and everything is fine except for the dashboard/admin area. It look like this with these error messages: http://www.emmareilly.co.uk/images/wordpress.jpg

I haven’t changed anything or installed anything except for an SEO widget (and the site still worked fine for a few days). My site is hosted with 123-reg.co.uk

I’m not a programmer beyond HTML/CSS so need some help with what to do.

Thanks.

Emma.