This fix is necessary for all systems (until Groundspeak repairs the map API entry).
In order to fix this issues you have to exchange two files in the Wherigo builder folder (c:\programs(x86)\Groundspeak\Wherigo\Builder)
If you follow the link you will get a zip-file that has 3 zip-files in it. I suggest to use map_v3_fox_avatar.zip. Copy the two files contained in map_v3_fox_avatar.zip to the Wherigo builder folder.
Should you receive an error message during your download attempt, you need to log in to the Groundspeak forum. An option to do so is provided on the error page.