Thank you for that great upload. I've been searching for a while now.
The CityNavigator 2010 is named "gmapsupp.img" and the topo austria is named "gmapsup2.img".
Both are on the 4GB mini SD card. If I delete one of them and only have one map with the name "gmapsupp.img" everything works fine.
The 4GB card works fine, so I guess there's something wrong with the naming.