fwrite ERRNO 22 with big (?) size

[hi1]

On linux the same call to fwrite works correctly (errno==0),
on windows i get ERRNO==22 if the "size" parameter is somewhat big (e.g. "103429"). :-/

see the code:

// first i open the file
FILE* request_file = fopen( pathname, "wb" );
if(request_file == NULL)
{
   // error
   return;
}

// second, try to write my buffer (already filled)
size_t written_bytes = 0;
if( parsed_request->body != NULL )
{
   errno=0;
   written_bytes = fwrite((parsed_request->body), 1, (size_t)(parsed_request->content_length), request_file);
   perror("fwrite");
}

// third, check fwrite return value
if( written_bytes < 0 )
{
	// write error
	return;
}
else if( written_bytes != (parsed_request->content_length) )
{
	// error - partial body received
	return;
}
// else fwrite succeed

NOTE:
if i replace "(size_t)(parsed_request->content_length)" with a small constant (e.g. "50"), fwrite succeed!

NOTE2:
I get the same behavior with "_write"...

P.S.
To give you more context details, i'm using the Mingw compiler.
I've defined the macro "_MT" to enable multi-threaded stdlib.
Maybe this has some side-effect on fwrite?
Since the call is not atomic with a big buffer, maybe fwrite fails to preserve thread-safeness?
I've tried to remove "_MT" in the makefile but fwrite still fails. :-(