I see mail coming in, can't open it and then it disappears when I refresh my browser

I see mail coming in, can't open it and then it disappears when I refresh my browser

This morning I checked my mail on Zoho.com directly; there were at least 4 unread messages that I could see but not open. When I refreshed my browser (Chrome), the messages disappeared completely! I know I saw them. The same thing happened in the last hour or so. I received an e-mail from Bluehost.com and that, too, disappeared. 

What is going on?