Page editing windows blank – no formatting toolbar

Site works from the browser end but problems when logging in to Admin. Initial problem was that both editing windows on all pages showed html code. After blog advice I deactivated all plug-ins and upgraded to 3.6. It resolved the problem and I now have a plain txt window and a code window. However, all page content is using a white font which leads you to suspect that the content windows are empty. Scrolling over the window as if to highlight text reveals the underlying content. The formatting toolbar has also vanished so I cant simply change the font colour back to black??? Any help would be greatly appreciated.