I'm using the Server-side Callback implementation. I used the first demo as a reference while writing my code.
Here is an example of the link I use as NavigateUrl: "/brokers/18/Shared Documents/Folder/FileName.png"
And here is the modified one: "Http://servername/brokers/18/Shared Documents/Folder/FileName.png"
I don't know if this can be helpfull but, if I try to get the NavigationUrl property on the server, even immediately after a node is created, I get: "Http://servername/brokers/18/Shared Documents/Folder/FileName.png", however, if I check the "a" tag on the client, the href attribute is still "/brokers/18/Shared Documents/Folder/FileName.png"