We're runnin version 1.8.4 of the phantastic Wassup plugin with WP version 3.8.1.
Unfortunately the 'show top stats' link under the Wassup Stats tab in the admin dashboard section doesn't work here. If clicked the window dims down to dark grey and a progress bar comes up for about a second and that's it. With the next click the page returns to initial state.
Probably someone knows a solution.