My firm is just now switching to Outlook and we are running into some annoying issues. If anyone has any experience with the following problem, I'd really appreciate some input.

We are using a third party COM add-in with Outlook and have followed Microsoft's instructions on how to register the dll's with Exchange so that the add-in will work as a trusted source and users will not get the Outlook security warnings when running the add-in.
In addition, we've also created a group policy to add a registry key that permits the add-in to behave as a trusted source. However, the security prompts still appear.

Any ideas?

Thanks in advance.
We've followed all the steps outlined by Microsoft.