Update for those of you playing along at home. I'm sending the same info to Stardock as part of my support ticket:
This is incredibly hard and frustrating to troubleshoot. The issue isn't limited to the combo of ShadowFX and Tiles. It's the combo of Tiles and any of several other autostart programs and services. Plus, the issue doesn't appear on every startup. For example, (with ShadowFX uninstalled) I was able to start my system with every single autostart item enabled, including Tiles, successfully. On the next reboot, the issue came back.
So I eliminated all of my startup programs and services and added them back one-by-one. I was able to add several back without the issue occurring, and I was able to get several successful restarts in a row in that configuration. When I enabled the next autostart program, the problem appeared again. So I disabled that most recently added startup item, which took me back to my known good configuration. When I rebooted, the issue appeared again! My stable, successful startup configuration wasn't stable any more. I had this same experience with several different combinations of startup programs.
I really want to use Tiles. It's close to me needing to use Tiles. 
I have found a workaround. I disabled autostart in Tiles, and when I boot to the Start Menu, I just click the Tiles tile instead of the Desktop tile to get to my desktop. That will have to do for now, until (or if) a fix is found.
Cheers,
Jeff
