Either the files "RADAR_MAP1.TGA" and "RADAR_MAP2.TGA are missing from the folder "imperial_campaign" found in the ...EB\Data\world\maps\campaign\, or you are playing with BI.exe. If you are playing with the BI.exe, then creating a folder called "barbarian_invasion" where the "imperial_campaign" folder is located and copying "RADAR_MAP1.TGA" and "RADAR_MAP2.TGA" into the "barbarian_invasion" folder should bring the radar map to normal. As I think that the BI.exe default to that folder when looking for information of the sort.