I'd first check Oracle client folder (probably c:\Oracle) might need some perms.
Make sure the account you are running sql as has read access to this folder and subcontents.
Also, if you are using oranames.tns file, and it stored on a network drive, you will need to copy that local to your server and update the registry to point to it. You may be able to get around that case if you use a domain account to run sql sever, give appropriate permissions and UNC path in registry. Havn't tried that before myself.