Activex error message

I have a web page that loads an activex control I made in VB 6. I recieved a call from a person that was getting an error message that said:

Could not load as a VCD file.

I've never heardof a VCD file. What is it and how can I solve this problem?

Thanks

P.S. The activex control is client side. It is downloaded to the client machine and they install it. Once installed they can view the page.