"Manual" upgrade from latest 1.8 release brokes dashboard because of invalid naming of plugins/Dashboard/templates/Dashboard.js file. Renaming it to dashboard.js (lower case) fixes the issue.
It should have worked OK as the source code only caclls for dashboard.js which is the same as the filename?
Oh, my bad. I updated from 1.7 and in that version the file was 'Dashboard.js'. And git somehow overwritten it with that name.