Spamming "You have bougth [ x ] silks"

Well i got a strange but cool bug at my server.
After charging silks you get spammed.

http://i41.tinypic.com/2i6cm04.jpg

Any idea how to spot this bug?
Would apreciate the help thank you Best forum.

That's php code that was workign so well since 3 months ago

PHP Code:

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$userName = $_POST['username'];
                $silkAmount = $_POST['silkamount'];            
                $orderid=mssql_num_rows(mssql_query("SELECT OrderNumber FROM SK_SilkBuyList"));
                $orderid++;
                ini_set('error_log','C:/logs/add_silk.log');
                error_log("$userID give $silkAmount to $userName");                
                mssql_query("exec CGI.CGI_WebPurchaseSilk '$orderid','$userName',0,$silkAmount,0");
                echo "<script>location.href='index.php'</script>"; 


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:cool:

Edit: Silks doesn't change any ammount... is just a visual bug.

cool :D