socket failing in Windows 7

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TCP/IP

I have the following code that has worked just fine up until Windows 7 (64 bit addressing):

int                 addr_fam = AF_INET; /* AF_INET6 behaves the same */
int                 socket_type = SOCK_STREAM;
SOCKET              conn_socket;

conn_socket = socket(addr_fam, socket_type, 0); /* Open a socket */

Currently, conn_socket is set to -1 and using WSAGetLastError() and FormatMessage I get the message "An invalid argument was supplied".

I have found nothing to suggest that this is all of a sudden an invalid combination of arguments but apparently, at least in my case, it is.

Does anyone have any insight into why this would be the case? Any idea how I can determine which of the 3 arguments the system thinks is invalid?

*** NEW INFO ***
This only occurs in DevStudio while in debug mode. The Release version of the code still works OK.