Dave,
I experienced this [DYN_WINDOW_EXCEPTION] problem for the first time this weekend. I made no configuration changes to the computer and I installed or uninstalled no software. I made no updates to the operating system or drivers. I tried shutting down all non-Microsoft process and made sure anything I was advised about early in the support process (VPN, etc.) weren't running (I have no VPN and I shut off what little virus protection I have). I've tried repairing the installation and I've remove and reinstalled the software twice - still nothing.
Windows 10, the latest version of Photo Mechanic - everything you would expect to be done by the end user as part of the troubleshooting process has been done or checked and it still won't run.
I think I am somewhat familiar with your issue. The component that is failing is attempting to create a port for inter-process communication on localhost (127.0.0.1) which should be achievable unless something denies it. This component has been in place and unchanged in this regard since it was written and was a part of Photo Mechanic 6/Plus before its release.
Something likely has changed on your system that is preventing this from happening.
EDIT: I just learned that the Camera Bits staff is out of the office until after Christmas. Leaving unresolved tech support tickets hanging is not acceptable for a company that claims to support professional photographers.
I also am on a well-deserved break from my work and here I am on my vacation, checking in on the forums and helping out on issues that don't require me to actually investigate and take time away from my visits with friends and family. Not all issues can just be handled immediately and preventing the support staff and engineering staff from a holiday break because there are unresolved issues is more than one can expect.
We are dedicated to supporting our customers as best that we can but there are limits to the free support that we offer our customers.
That said, I do have another suggestion that you could try:
Create another user account on your system and log into it. Does Photo Mechanic 6 fail to run with the same error?
-Kirk