VS 2008 [RESOLVED] UserControl does not display in IE32 on Win7

Hello, guys,

(See update at end of this message)

I have this nagging issue with a userControl embedded in HTML.
(Ok, Ok, I know I shouldn't play with fire!)

Here is the scenario:
-From a web site, a HTML page is called;
-This page embeds in its code an 'object' tag, referencing a DLL from the same web site.
-This DLL is a userControl class object.
The userControl was developped using Visual Studio, VB.NET: first under VS2003, then ported to VS2005, finally to VS2008.
The usercontrol is registered for COM, compiled for 'AnyCPU'.
And it's been working flawlessly for the past 10 years or so.

The workstations (on which this page is seen) use all possible versions of Windows, from XP and up.
Now, under Win7, I find that:
- IE 64 bits browser loads and displays the userControl;
- IE 32 bits (the default browser) downloads the userControl, but will not display the userControl.
Fiddler reports no error and the DLL is downloaded in the temp files folder.
It seems that, under IE 32bits, the DLL is not fired up in the 32bit environment.
I checked the registry for a possible difference between the two versions. No success.

Here is the code for the HTML page:
<html>
<head>
<title>This page to test the Viewer only (HTTP access only!)</title>
<link rel="Configuration" href="viewer.xml"/>
</head>
<body style="background-color: lightgrey; overflow: hidden;">
<object id="Viewer"
width="100%"
height="100%"
classid="Viewer.dll#Viewer.Viewer">
<b>Failed to load Viewer...</b>
</object>
</body>
</html>

code in the 'viewer.xml' file:
<configuration></configuration>

To simplify tests, an empty version of the viewer was built from scratch (in the crazy idea that I missed something on the way...):
-New project, userControl class, dock an empty splitContainer, set Com-enabled and compile.
-Add a project, of userForm class, dock the userControl, compile and run. Works OK.

I copied this DLL to the web site, then called this page from another workstation
This viewer displays and reacts correctly in IE64, but I get an empty frame in IE32.

My question is:
What possibly could block IE32 from loading/activating the userControl?

I looked everywhere for an answer to this puzzle...
Now, I turn to the community for help!
Thanks

UPDATE:
We figured that our IT dept has set some security features that block the DLL from working properly...
Case closed.