Can’t insert or format images

I’m attempting to add images to a page, which worked perfectly well yesterday, but today the image uploader appears without the size and position formatting options indicated. When I click ‘insert into post’ the image upload window closes and the name of the pic file (without the extension) appears in the page text but nothing else – no sign of the image.

Have tried this using Firefox and Chrome and have the same problem with both browsers. Anyone know what’s going on? I’d be very grateful for some help with this.