Follow Up: OK, the problem is gone now. After running several times through the cycle of opening the program, starting a custom scan, cancelling the scan, closing the program, the program suddenly functioned correctly on the fourth attempt.
Strange thing happened with my custom scan this morning. After selecting custom scan from the scan type selection page, the configure scan button appeared as it should. However, when I clicked the configure button it went directly to scan giving me no opportunity to select folders etc. This initial scan did not include a file system scan. When the scan was completed the finish button appeared. When clicked, the program went into a scan which did include a file system scan but again without any opportunity to select folders. When this scan completed, the finish button appeared. When clic