Windows XP SP2 - Outlook 2003 - installed Outlook Add-in but it does not launch

On other XP systems it launches with no problems.

1. C# Outlook addin, compiled with the 1.1 .Net Framework.
2. We have a Connect class that implements the
Extensibility.IDTExtensibility2 interface.
3. This addin loads fine in 99% of our workstations.
4. We have tracing in our code that writes to the debug stream in all the
entry points of our Connect class (i.e. constructor, destructor, and all
implemented methods). In the cases where our Add-in's toolbar does not show
up in Outlook we do not see any logging. So we don't think the Outlook
Add-in is being called.
5. The environments with this problem:
• Have the 1.1 .Net framework
• Have the LoadBehavior in the registry set to the correct value (3) to
enable the plug-in to be loaded by Outlook. After opening and closing
Outlook the value stays the same (3), so Outlook is not failing to load the
plug-in
• Have had the 1.1 .Net Framework uninstalled and re-installed to see if
this would help
• Have other 1.1 .Net applications that work.
• We uninstalled and reinstalled Office.
• We cleared out the registry entries.
• We don't see an entry for our Add-in in Outlook--View--Toolbar

Main questions: Is there a way to get debug trace from Outlook that gives us
some info about the plug-in loading process? What plug-ins did outlook try
to load? Which ones failed and why? etc...

These are some things we have already tried in Outlook:
1. Setting the Tools-Marco--Security level to low and un-checking the
check box in the Trusted Source tab.
2. Setting permissions on all the Add-in code installation files to
include everyone with all rights.
3. Turning debug on for Outlook -- There is no logging for Add-in loading.

Recommendations?

Tom