I spent several hours on this small problem. atlasglob.axd is a virtual page in Atlas, Microsoft's AJAX framework. It is used by several Atlas components and is created by the GlobalizationHandler class in the Atlas assembly. To get it to work you need to have the following line in your web.config:

<add verb="*" path="atlasglob.axd" type="Microsoft.Web.Globalization.GlobalizationHandler" validate="false"/>

this all worked fine on my dev box but when I first deployed my Atlas enabled web site to the live server it didn't work anymore. atlasglob.axd resulted in a 404. I triple-checked my web.config but it was okay, I looked online but no one had the same problem. I didn't install the Atlas framework on the live-server, I just copied the Atlas assembly into my bin directory, I was under the impression that should be enough.
In the end it struck me, as a security concious guy I always kept the script mappings on IIS to a minimum. So I opened IIS and checked the Application Mappings, axd was not among them. This means IIS never passes control over any *.axd files over to the asp.net runtime and the registered handler can never kick it. Adding the mapping fixed the problem. It also proved that you don't need to install the Atlas framework to use it on a machine, just put Microsoft.Web.Atlas.dll into your bin directory.