form suddenly not posting correctly yii

Question

it was working fine the past few weeks but i have no idea what happened... Every time I submit it gives me user_product_id cannot be blank.

<?php echo $form->dropDownList($model,'user_product_id', 
    CHtml::listData(Product::model()->findAllByAttributes(array('store_id'=>$store_id)),'product_id','product_name'),
    array('prompt'=>'Select Your Product'));
        ?>

Not sure if this is related to the same problem, but within the same controller, it also gives me an error saying trying to get non-object, when it is an object.

$model->target_id = Product::model()->findbypk($product_id)->name_id;

var_dump gives me an integer for $product_id as well as the entire expression...