I am working on a VSTO project for enhancing the old plug-ins for Outlook 2003. Actually, the plug-in is built on VS 2005. Now, I am trying to debug it on VS 2008.

Everything is working fine in the development box. It is also working fine in freshly systems ( OS ). But, when installed in the users systems, the plug-in is not working. The plug-ins are installing perfectly without any error. But, are not displaying in Outlook.

In some systems, it is installing and working well. But, suddenly disappearing. They are not displaying even if I install them again, in that systems.

They are also disappearing when other plug-ins are installed.

I have done the following to determine the fault.

* Given Full Trust to the assemblies using CASPOL, setSecurity project
* Given full trust to it through command-line also (using caspol.exe)
* Checked the registries in HKCU and HKLM. In this, CLSID, IntProcServer32 keys
* checked all keys in registry and every thing is set right there, including LoadBehaviour = 3
* Set the environment variable VSTO_SUPPRESSDISPLAYALERTS=0 and run the outlook from command-line
* Checked the PIA, VSTO runtime and .NET Framework in the client system
* Checked the privileges of user in client’s system

But, in vain. I couldn’t get a single clue for this abnormal behavior of my outlook plug-ins.

I have to solve this problem as soon as possible. Any suggestion is appreciated.

Please enlighten me what is happening and suggest possible work-arounds.

Thanks in advance!