Make sure you have all of the necessary iPhoto preferences relatated to places set properly, i.e. in the iPhoto/Advanced pane where the Look up Places should be set to Automatically.
Next, if needed, launch iPhoto with the Option key held down and create a new, test library. Import some photos and check to see if the same problem persists. If it doesn't then the problem is limited to your current library. If the problem persists it's system wide and may require the reinstallation of iPhoto.
Places had worked correctly before, and it appears that none of the settings were accidentally changed. Also, I'm able to view places as a list, just not as a map.
I did as you suggested and tried using a different library, but it still did not work. I guess a reinstall of iPhoto is my only option at this point?
Here is what I did to trouble shoot:
Checked to make sure my iPhoto was current
Checked settings to make sure they had not changed
Tested a second library (opened iPhoto while pressing Library) and saw the problem is with iPhoto, not my library
Removed receipts per this article: http://support.apple.com/kb/TS3249
Uninstalled and reinstalled iPhoto
Deleted the iPhoto cache in my Library
None of these worked
I looked at the post linked to above that said that Safari might be the problem, even though I never use Safari I first emptied the cache and deleted all cookies (though I think all you need to do is delete Google related cookies). This is working for now, hopefully it will continue to work.
I'm having the same issue and tried Richard Liu's fix. It does work BUT it's only temporary. When the library is closed and then reopened the problem comes back and will require another application of the "fix".
Richard reports that he's reported it to Apple and it's at tier 2 (?). So Apple knows about it and is working on a fix.