Wordpres Admin Menu (top) and all editors missing for pages and posts


I have a multisite install of wordpress which has been running for some time without problems. Most of the most recent sites are using Genesis templates and there is no problem with these.

Sites that don’t use Genesis themes such as the default wordpress theme are suffering from the following problem.

When the user (regardles of role) goes to edit or create a new page or post, the top wordpress admin menu disappears along with all the editors and windows in the first column (using 2 columns) the left hand column with publish buttons and page formats etc is still visible. The page editor and everything below is missing.

When using the Genesis themes this is not an issue.

Any ideas please?