Weird, I posted a reply yesterday but it didn't seem to come up.
7.7 M0 was no dice. I cleaned out any existing DisplayLink drivers (using the DisplayLink Cleaner Tool), and uninstalled any Lenovo Dock drivers.
Rebooted the Carbon, installed the 7.7 M0, and rebooted again.
Using the original Dock that was first attached to the Carbon:
Plugging out the original Dock, and plugging in another identical Dock:
