Page.TemplateSourceDirectory not working

It works locally on my Vista machine, but it returns nothing when I put it on a Server 2008 machine.  I have tried both code lines below to get the dir of the page that is being run, but it's giving me blank.  Any ideas why? 
strLocation = Page.TemplateSourceDirectory;
strLocation =
HttpContext.Current.Request.Path.Substring(0, HttpContext.Current.Request.Path.LastIndexOf("/"));
...