Stay or Leave Page pop up won't respond

I am having a problem and don’t think it is browser related because it happens on both Firefox and Safari.

While working on a page or post in the admin area, all of a sudden the pop up opens the one that says would you like to Stay or Leave The Page

It is non-responsive so I can’t get rid of it and have to force quit the browser and reopen it to get back to normal I am sure there is a bug somewhere.

I am on a brand new 27″ 2013 iMac with Mountain Lion and 32 Gb of Ram so can’t seem to figure out why this continues to happen. I will loose all the work I was doing so now I have to update the page every few minutes to make sure I don’t lose it again.

Any help would be appreciated.

Len