Problem uploading Excel-document. What's wrong?

For some reason, not all of Excel-documents can be upload from my computer. In half the cases get the error ".. no!! error:" from a block of try-catch .. What is wrong?

        private function importXLS(e:MouseEvent):void {
            fr = new FileReference();
            var fileFilter:FileFilter = new FileFilter("Excel (.xls)", "*.xls");
            fr.addEventListener(Event.SELECT,selectXLS);
            fr.browse([fileFilter]);
            statusLabel.text = "selecting...";
        }

        private function selectXLS(e:Event):void {
            fr = FileReference(e.target);
            fr.addEventListener(Event.COMPLETE, fileI开发者_如何学运维n);
            fr.load();
            statusLabel.text = "loading...";
        }

        private function fileIn(e:Event):void {
            ba = new ByteArray();
            ba = fr.data;

            xls = new ExcelFile();

            var flag:Boolean = false;
            try{
                xls.loadFromByteArray(ba);
                flag = true;
            }catch(error:Error){
                Alert.show("no!! error: " + error.getStackTrace());
            }
            if (flag == true) {
                statusLabel.text = "XlS loaded.";
            } else {
                statusLabel.text = "XlS didn't load.";
            }

        }

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You are reading the entire file into memory. If a user tries to upload too big a file, their browser will crash. Is there a reason you doing this? Are you using the bytes in the client or just passing them to the server. If you are passing them to the server, you want to just not use the fr.load method that you call in selectXLS(). Instead use fr.upload and avoid your whole problem.