Unable to log in to time capsule wired to an router after reconfiguring that router
FWIW, this is how I ended up logging in to administrate the time-capsule.  

I cabled the TC to a laptop using one of the three LAN ports on the TC.  At that point Win7 indicated there was something connected at something like 192.168.1.1, which I suspect is the TC's default IP address.

Using that IP and the existing password, I was able to log in to administrate the TC via AirPort > File > Configure Other.

I suspect that on power-up, TC uses that default IP address until it successfully connects through it's WAN port using DHCP, or in my case, the user-configured fixed IP.

Anyway, with a successful login via AirPort, I was able to update the fixed IP to one that was in the range of the reconfigured netgear router to which it is WAN cabled.