Problems with attaching references by URL

[thanby]

Environment: AutoCAD Architecture 2010 and 2011

I'm working on a way to publish many of our drawings online, and I'm trying to fix the issue of x-refs by replacing them with URLs to the references instead of their normal UNC path. In theory this should be a breeze, but I've run into a brick wall. In both 2010 and 2011 (tried with fresh installs, and with update 2 on each) the only way a reference can be attached is if it has first been downloaded (usually to the temporary internet files directory). Otherwise after entering the URL of the reference AutoCAD throws an "ATTACH - Invalid File" error that says the file is corrupt.

According to the user documentation, it should be as simple as providing the URL, with no download necessary. If all the references have to be downloaded first, it defeats the purpose of using URLs instead of UNC paths. The documentation is here.

Does anyone have a clue about how to fix this? I read a brief bit about dealing with version changes, but I tried to eliminate it by trying with fresh installs, and then trying again with update 2 applied. Same results either way.

Thanks for any help you can provide!