I wanted to post a solution to an issue that comes up every time I have to setup a new developer in our organization:
Could not load file or assembly 'AjaxControlToolkit' or one of its dependencies. Access is denied.
My solution is to grant Full Control to the "Everyone" group to the folder C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files
I know there are other solutions to this problem, but this one seems the simplest for me.