can't see right hand end of tracks in project window

In a Cubase 5 project I suddenly no longer have access to the right hand end of tracks. The tracks go right up to, or beyond the right hand edge of the window, so that I can no longer select the track handles and lengthen the tracks by pulling them to the right. What setting have I accidentally changed? I’ve been using Cubase for years and have never encountered this problem before.
Any help would be appreciated.

Have you tried clicking on a track and using the mouse wheel to zoom in or out?

Regards :sunglasses: