Best thing to do in this situation is delete your TopoFusion.ini file, to get rid of the erroneous path.
delete your settings file, it probably has a bad path.
To reset back to default settings, delete (or rename) the file TopoFusion.ini. It should be here:
C:\Documents and Settings\*Your USER NAME*\Local Settings\Application Data\TopoFusion\TopoFusion.ini
I am not sure how a bad path is getting in there, but it seems it happened to Bob Bailey and to you as well. Maybe send me your TopoFusion.ini file before you delete it and I can take a look.