Response.Redirect with virtual path (~) and IIS

Question

I'm experiencing a strange error in my deployed web app. I dont have much control or insight into how IIS has been set up so I'm in the dark a bit. (When I tested I used virtual directories)

It appears that when I call Response.Redirect("~/") from one page the domain of the page that is being redirected to changes

e.g.

when I call Response.Redirect("~/") from http://URL/TestApp/ I am redirected to http://URL/AnotherFolderName/

I'm wondering if the AppDomainAppVirtualPath property is kicking in when ~ is used and this is not hooking up to IIS properly?