Can't save due to "Multiple Tabs/User Issue"

I updated Microthemer today and after doing that (woe of woes), Microthemer now won’t let me save anything – when work on a new selector I am told in upper right hand corner that “settings failed to save” and I get a popup box error message (on both Chrome & Firefox) that says in the box multiple tabs/users issue and indicating that MT settings were updated more recently by another user or browser – even when only one tab shows up on my internet browser. I am also emailing you via the supprt email a screencapture of the MT error message so you can see it exactly.