ASP.NET 2.0 VS2005 MasterPage doesn't always show an image

I have an ASP.NET application that uses a MasterPage. In the MasterPage I have an image. This displays well on the development environment and on the default page that inherits it. But now I have set the website to prompt for a login using Form Authentication. The Login page 开发者_开发问答also inherits MasterPage but it can't seem to find the image. Both aspx files (default and login) are in the same directory as the MasterPage. There is only one image placed in the Images folder. Has anyone seen this before? Any ideas on how to fix this?

Thanks in advance, Rob

---

I have used the following to allow all users (even unauthenticated users) to access files in the images folder.

<location path="images">
  <system.web>
    <authorization>
      <allow users="*"/>
    </authorization>
  </system.web>
</location>