Flash sendAndLoad problem?

[hooligan2001]

Just curious as to way this would happen? I have one send and load that looks like this

function checkDetails() {
    loginDets.user = mc_login.txt_username.text;
    loginDets.pwd = mc_login.txt_password.text;
    _root.acDetails = [mc_login.txt_username.text,mc_login.txt_password.text];
    loginDets.sendAndLoad("http://localhost/test/process.php?ck="+new Date().getTime(), loginResponse);
}
//sender
loginDets = new LoadVars();
//reciever
loginResponse = new LoadVars();

loginResponse.onLoad = function() {
    if(this.authen == "ok") {
        //load the users data in
        _root.userDetails = [this.petname, this.petlvl, this.petexp, this.usermoney, this.userskill];
        t = this.inventory.split(",");
        y = this.stat.split(",");
        SplitUserItems();
        SplitUserStrength();
        play();
    }else if(this.msg == undefined){
        _root.error("Message recieved - cannot find page");
    }else{
        _root.error("Message recieved - "+this.msg);
    }
} 

and then a php script that finds the user name and pass and returns their details. Now this works perfectly fine. But now I tried to implement a new sendAndload so save user details that they may have change to the database, it doesn’t work. Not matter what I try it doesn’t get any returned variables. The scripts are pretty much identical. Cant figure out why.

Can you have more then one sendAndLoad in the same swf that request a different page?

And is their a max number of variables that can be sent?

What are the basic problems to be aware of when using sendAndLoad ?