Password change disabled Master Password dialog box in Firefox

Password change disabled Master Password dialog box in Firefox

I opened my Home Page (zohomail) today and got an announcement/suggestion to change my password due to the Heartbleed Bug. I changed the password but now it appears to have somehow disabled my Firefox master password dialog box, i.e. when a password is changed on any site this box will pop up asking for the Master Password so that the new site password can change.

I reset passwords on two other sites today and the function works as it should elsewhere, the problem--somehow--seems only to occur here. My Firefox and all other relevant software is up to date, and zoho is not blocked in any way with cookies etc. The only thing that has changed from yesterday to today is I changed passwords as suggested.

What could cause this, and how to remedy? Could the new zoho encryption in response to Heartbleed be the culprit?