Somewhat odd problem networking TC

Question

Hello - I have a Timecapsule which I am using to back up a variety of Maclaptops and desktops; it also serves as my router and wifi. A little while ago, I tried using my airport express to extend the network (I have a separate structure on my property which serves as an office). All **** broke loose after I attempted to use it (I was unable to get on my network, the DHCP assigned was wonky, etc, etc). I have since discarded this attempt with the Airport Express. HOWEVER, there is a weird residual effect - it does not see the Time Capsule by its correct name - for example, under time machine preferences, it tells me I am backing up my information to share 'Data' on volume 'Glenns-airport-express,' The time caspsule is named 1579TC1, and in fact is reported as such by my other device. A further hint is that when I attempt to mount the volume in Finder, I first get the message 'resolving alias,' which is then followed by a successful mount of the directory structure.
What gives? I suspect an explanation for this might also help explain some of my earlier weirdness (which is contained in a separate post).

Answer 1

I think BDAqua was headed in the right direction (IP
address change being the root cause). Try this: go to
Keychain Access and delete any entries that pertain
to that PC.
Forgive my ignorance - I don't think I see any entries pertaining to the PC. There are a bunch of certificates that look like they are from the internet. Nothing else. I have always just connected to the PC as a guest without a password.