Sincere thanks, Ken and canuck for taking time to test for this glitch.
When I posted my problem to the Forum, I had expected my issue to be the direct result of an overlooked setting, so I didn't think to conduct my own experiment with a different clip.
A few minutes ago, I started fresh with a New Project and placed a different clip all by itself on the main Video Track row. When I split that clip with the scissors, there was no automatic audio fade-in. VS Pro X5 was performing exactly as it should.
However, I then added the "problem clip" to the main Video Track row immediately following the "good track". When I split the "problem clip" with the scissors, an unwanted audio fade-in occurred automatically as before. Thankfully, splitting the "good clip" still does not cause an automatic fade-in, even with the "problem clip" co-existing on the same track.
Clearly there is some quirk inherent in that clip that was imported from a DVD. As a workaround, I'll edit my complete project with no regard to those unwanted fade-ins and then take time to adjust the audio in one swell foop as a final step.
VSP X5 126.96.36.1998, CPU i7-860 Lynnfield, 8GB Corsair 1600 DDR3, NVidia GeForce GT240 1GB Video, Samsung 1TB HD, Win7Pro 64bit, MSI P55-GD85 Mobo, LITE-ON IHAS-324-98 R SATA 24X DVD Burner, Hanns-G HH-281HPB 27.5"LCD Mon, OCZ 700W PSU, DirectX 11.0