WordPress edit screen error

when i go to edit pages in in my wordpress dashboard the screen ends up funny.

i.e the side widgets showing publish etc on the 2 column screen cover part of the main text field and the side scroller of the main text field, does anyone else have this problem or know why its caused?

I do have screenshots which show the error better if anyone needs to have a look.

Any help i can get would be appreciated.

Thanks

Dave