OK, the problem is solved.

I had been a former customer of the iFinity Url Master module, and so assuming that the AUM logic is very similar to its predecessor (Url Master), I went back and read through Bruce Chapman's "Parameter Redirection, Rewriting and Replacement with Url Master" document from Url Master 02.08.00.  Wow!  This is a much more complex topic than I had initially realized!   By the way, this is a great document to get grounded in the theory of how DNN manages URLs for anyone else that's interested.  It would make a great Wiki article on the DNNSoftware.com site.

I dug in and found the source of the problem.  The product catalog module used a GridView control to page through the list of inventory items.  The code to navigate to the next page in the control was manually appending the page parameter into the URL in folder format (e.g. /pg/2/) rather than query parameter format, and then it was redirecting to itself with the updated URL.

To fix the problem, I edited the code so that the GridView page index was changed without editing the URL and initiating a redirect to the updated URL.

Before:
Protected Sub GridView1_PageIndexChanging(ByVal sender As Object, ByVal e As GridViewPageEventArgs)
    Response.Redirect(GetPageIndexUrl(e.NewPageIndex))
End Sub
(The GetPageIndexUrl routine is where the URL gets modified.)

After:
Protected Sub GridView1_PageIndexChanging(ByVal sender As Object, ByVal e As GridViewPageEventArgs)
    Me.GridView1.PageIndex = e.NewPageIndex
End Sub

Bingo!  Now the user can page through the GridView control with AUM enabled.  The code seems to be a little more efficient this way, too.

See Ya!
Van