Gray screen when deleting a flow in Flow Designer

Problem

When I try to delete a flow in Flow Designer I just get a gray screen and everything seems locked up.

Environment

All versions of xMatters

Resolution 

Look for any popup or ad blockers in your browser and disable them for the xMatters web user interface.

Cause

An overlay or popup blocker is preventing a warning screen or modal from coming up. While it looks like things are hanging, it's actually just a dialog box that needs you to confirm deletion of the flow.