The wireshark forum shows that if you run wireshark from the command line you get this error..
(process:1234): Gtk-WARNING **: Locale not supported by C library. Using the fallback 'C' locale. (wireshark-bin:1234): Gtk-WARNING **: cannot open display:
… for which there are a couple of work arounds, such as setting your display variable or opening wireshark from within an xquartz terminal window.
The actual fix was found here, notice the log out after installing… by simply logging out and back in again my wireshark now loads without any nasty work arounds.
Hope that helps!