I have had repeated problems with my WP dashboard disappearing, or at least elements on of it. When I trouble shoot plugins I would usually find some combination that would make all the widgets reappear, but not always. The dashboard would look like this:
One day I noticed that I had a lot of Spam (noted by the red “SPAM” on the Dashboard) and clicked on the link to see what was what. I emptied the Spam and when I returned to the Dashboard, all was well!
So there is my WordPress tip of the day for you. If you Dashboard has gone wonky empty your Spam. I cannot guarantee that it will work 100% of the time for you, but so far it has for me. (Still, I wonder what is in that Spam causing the problem…)