Host was not found error in PH Web

[Edis, Bob]

G'day all

PowerHouse 4GL 8.21D
PowerHouse Web 2.21D
Windows NT 4.0 sp6
IIS 4.0

We have replicated our PH Web environment on a test box.  We copied the
programs, source and compiled, Quick and HTML, from the production box to
the test box.  The IIS configuration and PH Web dispatcher configuration are
identical on both machines other than references to host machine names.

Here is the problem:
We open a screen from a HTML menu page and click on the Search button.  A
list of records is returned with the key item hilited so we can select a
particular record.  In the production system we are returned to the first
screen with the fields filled in using the record selected from the list.
On the test box we get a Proxy error:

Proxy Reports:
11001 Host was not found

The host specified in your URL could not be found. 
This error could have been caused by: 
*	Bad / misspelled URL 
*	Following an invalid link 
*	Your network connection and/or transient conditions on the Internet 

The host specified in the URL is the same that allowed into the first search
screen so that's OK.

Any ideas where we should look to find the source of the problem?

Regards to all,

Blue