Zoho shutting down when I save a tab

Zoho shutting down when I save a tab

In the Leads and Contacts tabs, once I add or edit a new record and then hit save, the whole browser tab shuts down. Happens in Firefox and in Chrome, so it's unlikely to be my browser.  Seems to only have happened today.  I don't know if it's because I've been adding custom fields and playing around with the record layouts, or whether it's a bug from an update released onto the software.

Is anyone else having this problem?