@bchliu: I saw this problem, and I suspect it may be related to having browser-switchboard installed. Do you have this installed?

Try starting evopedia, launch MicroB after evopedia closes its window, type http://127.0.0.1:8080 into the address-field. That works for me. If you are familiar with a terminal-editor, you can edit /usr/bin/evopedia.sh and replace the long dbus-command with just
browser --url "http://127.0.0.1:8080"

PS: if MicroB is already open when you start evopedia, it tries to access the localhost-server too fast (before it is fully running), just reload the page and it should work…