I talked to Cakewalk Technical support today (via phone) and the tech didn't seem to have a problem with X1 being installed on the D: drive. But (on the other hand), he couldn't tell me why the error was happening. So, I've got that going for me.

As Sherlock Holmes used to say, "It's the C: drive, my dear Watson, the C: drive."

Thanks again to all of you.

Take care.

-Jeff-