When you go to File > Site Import do you see the panel for importing? Are you able to click on the go button to configure the import? When you finish configuring the setting the import should begin, is it just taking an unusually long time to run? If it sits there for more than a few minutes without updating then something must be wrong.
You can try clearing the cache to see if this has any effect, here are some instructions to do this:
Please post back and fill us in on the details so we can determine what to do next.