My VB application can not find a registered dll? It is a COM dll developed by someone else.

I have a system that has a dll registered, and other programs use it just fine.
I'm developing a VB app in VB.net 2003 and it runs find on the dev machine that does not have the dll registered, but when I copy it over to the main system (with the registered dll), it gives the common error it can't locate the dll.

I also have a copy in the local directory with the .exe
I'm not sure what else to do, I did not make the dll and I do not have the source.
I tried re-registering the dll and it made no difference.

System.IO.FileNotFoundException: File or assembly name Interop.ETHERNETDETECTORGENLIBRARYLib, or one of its dependencies, was not found.
File name: "Interop.ETHERNETDETECTORGENLIBRARYLib"

any help would be great!