Static Front Page has gone blank

After working fine for a long time my Front Page is completely blank. The page sometimes flashes up for just a split second and the favicon is OK. If I add /home/ to the URL it loads fine. If I select a different page as Front Page, that goes blank and I can see the old Home page.

Following other threads I have checked that there is not a rogue index.html on the root and there is nothing on the error log.

The admin is fine and I can edit the home/front page. Can anyone throw any light, please?