Error connecting to an oracle database using Microsoft's data provider for oracle

Hello, I have been using the provider for some time without a problem. However, when one of my co-workers tried setting it up on his computer, he gets the following error when connecting to the database: "Unable to find an entry point named OCIEnvCreate in DLL oci.dll" He can set up the connection in the server explorer without problems. He can even open tables in the server explorer. But any time he tries through the application he gets this error. Does anyone have any ideas how to fix this? Thanks