This should honestly be a sticky. It is quite disappointing that Roku (including moderators) have not addressed this issue more openly since it seems to be a fairly common yet devastating problem.
Wireless not working.
When setting up a wireless connection the the list of networks is blank.
Pressing select on the blank screen will result in the Roku restarting.
The MAC address comes up as all zeroes.
1.Push and hold the reset button which is on the rear side of the Roku player.
2.Release the reset button after 30 seconds
3.Unplug and reconnect the power cable after 30 seconds.
4.Redo the setup of the player.
Unfortunately it seems for most people the only solution is to get a replacement unit.
I did want to address one further problem I have noticed. Roku should really replace units even if they are over one year old. This issue seems to point to software/firmware only due to the fact that there are so many cases popping up in the same time frame. I suppose its possible that its a batch of bad wireless components that happen to fail at the same time but very unlikely since it ranges across different models and production dates.
If anyone has any suggestions to add please post along.