What are some reasons why an OCX can't be registered on a PC?

I have a client running Win98 and they can't register a third party OCX on their PC. Our setup.exe has successfully installed and registered this OCX on hundreds on PCs. However, this client can't get the OCX registered.

When they run our app, they get an OLE error. When they try to manually register the OCX, they get an error.

What kind of things cause this to happen.

Thanks,

Jerryt