"file server is running on your machine" message

Question

OK, this seems very weird & I can't figure out if the issue is in my new (simultaneous dual band) Airport Extreme or the Mac (iMac G5) I use to administer it.
When I try to connect to a USB drive connected to the Extreme from my iMac, & the iMac is connected to the Extreme by ethernet, I see the Extreme in the sidebar of Finder, but when I click on it to access the drive, I get a "connection failed" bar across the top of the Finer window. If I click on the "Connect" button at the end of that bar, I get the following message:
"This file server is running on your machine. Please access the volumes and files locally."
The volumes (the drive is partitioned into two volumes) are not showing up as local ones (in the "Devices" section of the sidebar), so I can't access them "locally."
BUT, if I turn on Airport on the iMac, I get the normal "Connected as ..." bar & the volumes appear as expected in the Finder.
The really weird part is if do not turn on Airport & I use the "Connect to server..." Go menu option & enter "afp://Extreme's_name.local" it connects & either or both volumes mount on the desktop as expected. ("Extreme's_name" is the actual name I have given the device.)
Weirder still, if I have one of these volumed opened in the Finder & click on the Extreme in the sidebar again, I still see the "Connection Failed" bar across the top +yet the volumes are there in the Finder window+, can be opened, & otherwise behave normally.
This behavior persists until I click the eject button in the sidebar, at which point the "Connection Failed" bar reappears & the volumes are no longer listed or accessible. Waaaaa?
FWIW, my MacBook has none of these symptoms. Whether connected by ethernet cable or wirelessly, clicking on the Extreme in the sidebar results in the expected "Connected as ..." behavior.
I tried researching the "running on your machine" message on the web & found some references the problem in connection with Windows (smb) sharing. Sure enough, looking in my keychain access file, I saw several passwords for the Extreme with the "where" info as smb://Extreme's_name. However, deleting these (& even all Extreme-related entries) had no effect.
I'm stumped. Any help or even just a clue would be appreciated greatly.

Answer 1

I seem to have eliminated the 'connection failed' problem & its accompanying 'file server is running on your machine' message as follows:
My Extreme was set up for its DHCP server to assign local IP addresses in the 192.168.2.100 to 192.168.2.199 range. This matched how my old SMC router had been set up for years. The SMC's DHCP server was set up to always assign 192.168.2.100 to my iMac's Ethernet MAC address. I did this because my iMac was set up as a webDAV server to publish an iCal calendar on my local network, using the address "webcal://192.168.2.100/ical/MyCalendar.ics." This worked fine with both the SMC & the Extreme.
I'm not sure why I decided to try it, but I changed the Extreme's DHCP server to assign local IP addresses in the 10.0.2.100 to 10.0.2.200 range. Obviously, this invalidated the address for the published calendar, but the iMac now connects to the Extreme's drive without any problems. (For those who care, changing the calendar's published address to "webcal://MyMac.local/ical/MyCalendar.ics." fixed that issue -- IOW, substitute the computer name for its local IP address. I probably should have done that to begin with, but hindsight is always 20/20, right?)
So my problem is solved, but I still would like to know why this worked. AFAIK, either IP range is equally valid for private networks. Any comments would be appreciated.