Bad Param Error (-4)

I just migrated my Dell XPS to Verizon FIOS using an ActionTec M1424WR modem/wireless router. I lost visibility of my two Airport Expresses connected to remote speakers...so I took one and hooked it up via Ethernet and launched the Airport Express Assistant. I ultimately had to do a hard reset on it since it wasn't being recognized even over a cabled connection. It now sees the AX, requests a password (now using the default "public"), then I get the following message:

Cannot read from base station.
Bad Param Error (-4)
Click the 'Back' Button to try again

I've tried again many times, reset several times, still no luck.

What do I need to do to get Airport Express back on my wireless network?

Thanks!