DM: Thanks, I fixed it by pulling off the impossible. I got Win 7 installed on an Asus Z390-E mobo (not supposed to be possible) with 3.1 USB drivers, updated, activated, virus free and totally rocking. MS did everything in their power to prevent installing Win 7 on my hardware but I was once a nerd and I came out of retirement for this one. Then, when I put Sonar 8.5.3 (the revered version) back on, all was well with the default buffer sizes.
For my next machine, I'll go back to SCSI (15,000 rpm and more reliable) as my data drive. I'm already running an SSD.