On 4.5.3 I'm getting a strange 302 redirect error.

Here's the scenario - I've created a thumbnail.aspx that displays and image pulled from the db based upon the ID in the query string - this is pretty standard stuff.  The aspx lives in the root of the DNN instance - the pages in DNN that are using it are referencing it with a root path ie: src="/Thumbnail.aspx?ID=10".

The page works perfectly for parent portals - IE Portals that are accessed thru their own alias. But if you access it thru a child portal then for some reason the aspx returns a 302 error (only on some of the calls).

For example I have a portal with an alias Wizard. Then I have another portal with two alias's the first being Wizard/b829 and the second being ThumbnailTest. If I access the thumbnail.aspx via the alias Wizard/b829 then I get random 302 redirects to the same page (thumbnail.aspx). I know this because I see the redirects returned when I use Fiddler. If I access the same site with the same user via the ThumbNailTest alias - it works fine.

One other thing - the page that calls this aspx is available only to authenticated users. When I access the site thru the  Wizard/b829  which is having the problem, the user authentication is blown out - if I refresh the page, or navigate to another page, I have to reauthenticate. On the ThumbnailTest alias, I don't have this problem.

Does anybody have any potential insite? This is driving me bonkers.