Ok, I did as AX suggested,
"I would like you just insert 1st disc, let it scan, Source field updates, remove the 1st disc w/o extracting, add a second disc, let it scan, does the Source field update or does it stay at "Please insert ....." and hang ?"
All 4 discs scanned appropriately, the source field updates as the drive spins up, almost immediately. No hang. No problems whatsoever.
Again, this with v.6.2.2.0 Beta (retail), Win7 64-bit