It is possible that the error is on my end but thought I would mention
the error in case anyone wants to save some download time.
First I downloaded this file and had a crc error when I tried to unzip (using 7zip on win)
http://www.ibycus.com/ibycustopo/IbycusTopo21iso.zip
then I downloaded the other file and had no problems with the unzip.
It also loaded into mapsource fine
http://www.ibycus.com/ibycustopo/IbycusTopo21.zip
From what I've seen, it's on the server hosting the maps. Some people will have grief with them due to the size of the file download.