Can't connect to localhost

[Mark Phillips]

I use my laptop for plone development. When I am connected to a network 
(wireless or wired), I can access zope and plone from my browser at 
localhost:8081. However, when I am not connected to a network (wireless or 
wired) I cannot access zope or plone using localhost:8081. I get page not 
found as the error. Plone and zope are stock installs from Debian packages.

These addresses work when connected to a network but not when disconnected:
http://localhost:8081/manage
http://localhost:8081/plone-site
http://localhost:8081/

I have tried the following:
1. Changing the ip-address settings in zope.conf from commented out to 
127.0.0.1 and I get the same error

2. ifconfig shows that lo is up and running on 127.0.0.1

3. A network testing script I have reports that lo is up and running at 
127.0.0.1

4. ps aux | grep zope shows it is running just fine

It may be a routing issue, but I just can't find the problem! I don't think it 
is a plone or zope issue, but it could be.

Thanks for any thoughts provided.

Mark