Internet Explorer cannot 'fully' load ActiveX Control

Context

I am migrating an installer for an ActiveX control from Per-Machine to Per-User. I did this by programming the installer write to HKCU\Software\Classes instead of HKLM\Software\Classes.

Problem

On my machine (Windows 7 with UAC Enabled), the ActiveX control successfully loads. On the other windows 7 test machines (one with UAC enabled, one with UAC disabled), the control 'partially' loads.

What is Partially?

When a user visits a page with the ActiveX control, Internet Explorer displays a warning message in a yellow bar on the top of the window. If you click the 'Run add-on' button in the bar, the control becomes visible and begins to run, but Javascript code that tries to access properties of the control return the error: Library not registered.

Differences between machines

On the dev machine reads from HKCR\CLSID\<GUID> succeed while on the test machines these reads fail. Reads from HKCU succeed on both dev and test machines. Reads from HKLM fail on both test and dev machines. (I collected reads using Sysinternals Process Monitor) Strangely, the keys that Internet Explorer fails to read are clearly visible if I use regedit to view HKCR\CLSID\<GUID> on the test machines.

Question

What can开发者_如何学Python I do to get the per-user control to load on the test machines? What could cause this difference between the dev machine and the test machines? Why can I see the key in HKCR with RegEdit but Internet Explorer cannot see the key?

Any help is appreciated. Thank you.