Can you temporarily relocate the TViX much closer to the AP (and turn on SSID broadcast) to make sure that the M6620 has enough signal that it should be finding the AP? If that fails, I'd RMA the unit (after making sure that it's one that's supposed to have the built-in WiFi).
If you're just using the TViX as a PVR and not playing or sharing files over your LAN, then what Aleron says is right, you don't need the LAN connection.
@TPeterson: You and Aleron maybe right, if Wi-fi only gives me the ability to share files, which I am not looking to do, then I may just cut my losses and forget about wireless. Everything else looks like it works OK.
Thanks for the help with this, I'm glad I found this forum and the smart people who are on here!