MP Navigator EX 1.0 & Leopard

Aged rank beginner upgraded to leopard, lost the scanner(Canon MP 970) and downloaded Canon's modification for the scan program MP nav EX. The scanner jumped back to life with the simple press of the scan button on the printer. Today, four weeks after the download, I am unable to scan from the machine and have to open MP nav EX manually. I looked at image capture and could not find a way to ask it to open MP nax EX as my default scanner. Any help or suggestions appreciated. Oh yes, I also have VueScan (for photos) in my applications base. Is Interference possibe ??