Between the trouble I'm having and the number of things that turn up when I google the issue, I'm really inclined to suspect that Microsoft has intentionally sabotaged Windows Update for Win7. Maybe it still works right for machines that are in constant use, and not just turned on once in a while? Seriously, checking for updates should not be a multi-day process. And when I boot up my Win XP VM that's hacked to impersonate Windows for Cash Registers, and check for updates? That goes smoothly.
In other irritation, I just noticed that the Kinetis KEA64 MCU has one-each external-interrupt input, and the only pin from which it can be routed is the same pin that's used for RESET. Really? Does no one ever want to have both a hard-reset input (for, e.g., debugging) and an IRQ input for the application? Oh, well: guess I either poll a GPIO pin from the background task, or figure out how to use a KBI pin (which Processor Expert seems to be telling me won't work).