A recent customer issue came up where they were load balancing servers but we unable to get the true client address logged in their IIS logs. They had their servers fronted by a BIG-IP and wh...
That could be a lot of things. First, I would go to the directory where the dll is located with explorer and make sure that the IIS user has access to the file.
Otherwise, you can look into the evert viewer to see if there is information about the load error in there.