Airport Extreme Base error -6753

My Airport Extreme Base quit working after I attempted to install and Airport Express base as a wireless system extender. I am using a PC with XP Pro.

The message is - an error occurred trying to access wireless device.......error -6753

Its all new equipment. The base and wireless system worked well for a week before I attempted to expand the system. I added a wireless printer with no problems earlier in the week.

I have tried a hard reset of the device. plugging and unplugging. Same message every time. Airport Utility sees the base, knows its name, but cant access it.

Not sure what to try next.