Ajax message error: NETWORK_ERR: XMLHttpRequest 101 exception

I have the following ajax entry:

$.ajax( {
    type: "POST",
    url: "http://192.168.7.9/api",
    dataType: 'json',
    data: { username: "john.doe", password: "123456", method: "search_samples" },
    success: function ( data ) {
       // Never get here
    },
    error: function ( XMLHttpRequest, textStatus, errorThrown ) {
        // Always here: if async true, errorThrown has no message
        // otherwise I se the NETWORK_ERR message
    }
} );

It returns with this error: NETWORK_ERR: XMLHttpRequest 101 exception.

I read a bunch of SO posts about this error, most of them suggested that I set async to true. This will delete the error message, but it is still an error, and I never get any reliable data. It seems to be just deleting an error message that doesn't help.

In a violinist, on the same dev machine, this works great - is this a problem with chrome? Origin problem? Is there something wrong with my syntax?