Security Error in WMI Connection

When trying to fetch running process details from a Windows 2008 server, I get the error code -2147217405 (0x80041003). I've read that it's a security issue. I'm connecting using a C++ MFC dialog-based application and have performed the following steps:

1. CoInitializeEx()
2. CoInitializeSecurity()
3. CoCreateInstance()
4. CoSetProxyBlanket()

hres = CoSetProxyBlanket(
            pSvc,                        // Indicates the proxy to set
            RPC_C_AUTHN_DEFAULT,         // RPC_C_AUTHN_xxx
            RPC_C_AUTHZ_DEFAULT,         // RPC_C_AUTHZ_xxx
            COLE_DEFAULT_PRINCIPAL,      // Server principal name 
            RPC_C_AUTHN_LEVEL_DEFAULT,   // RPC_C_AUTHN_LEVEL_xxx
            RPC_C_IMP_LEVEL_IMPERSONATE, // RPC_C_IMP_LEVEL_xxx
            NULL,                        // client identity
            EOAC_NONE                    // proxy capabilities
        );

I haven't used the COAUTHIDENTITY structure to provide credentials for setting the proxy security.

Thank you in advance.