The Alert points and Placemarks are different things in iGO. The alert point is not POI!
The first comes from content/speedcam, but the second comes from content/POI
Look inside the speedcam folder and remove unwanted *.txt files and the speedcam.spdb file (SpeedCamUpdates.spud is the container of your own alert points).
At next launch the iGO builds up the new database from remaining *.txt files.