"project.resources.url" doesn't seem to support Authorization like:

project.resources.url = http://admin:passwd@myservername/myresourcetest.yaml

And when you click on "Update Nodes for project" you get the ERROR:
"Error updating node resources file for project examples: HTTP Authorization failure"

Troubleshooting:

With Curl:

$ curl -u admin:passwd "http://192.168.222.111/hosts/myresourcetest.yaml"

The request is:

GET /hosts/myresourcetest.yaml HTTP/1.1
Authorization: Basic YWRtaW46Y3hhbmdlbWU=
User-Agent: curl/7.15.5 (x86_64-redhat-linux-gnu)...
Host: 192.168.222.111
Accept: */*

And from Rundeck, with the following setting:

project.resources.url = http://admin:passwd@192.168.222.111/hosts/myresourcetest.yaml

The request is:

GET /hosts/myresourcetest.yaml HTTP/1.1
User-Agent: Java/1.6.0_20
Host: 192.168.222.111
Accept: text/html, image/gif, image/jpeg, *; q=.2, */*; q=.2
Connection: keep-alive
If-Modified-Since: Wed, 20 Jul 2011 14:04:54 GMT

---

So as you can see Rundeck it doesn't send the "Authorization" header in the HTTP request.