Wireless "N" LAN adaptor connection problems with ActionTec MI424 Rev C

[#1]

Two different type N wireless LAN adaptors work fine in the same room with the ActionTec router connected at 54mps using type "G" connection.  But when moved upstairs, connection speed is 117kbs which is clearly a type N connection.  IP address is assigned correctly, but cannot even ping router.  So I think lower signal causes the type N adaptor to try to connect with "N", and the ActionTec accepts the connection, but since it doesn't support "N", there's no real communication.

I see the initial connection speed at about 17kbps, but within less than 1 second, it goes to 117.  So my guess is the connection was made with type G, and the LAN adaptors switch to "N" due to the poor signal, but can't communicate since the ActionTec doesn't support "N".  But I would think the ActionTec would tell the LAN adaptor it can't use "N" and it wouldn't switch.  There's no option on the LAN adaptor to restrict it to use only "G".

This equipment and location has worked before.

Is there a software update for the ActionTec to fix this?  Or is this something that must be fixed on the LAN adaptors?