i'm having problems with echmultiselect in my project, it doesn't filter at all and inhibits other column filters already working.
View
    array ( 
            'name'=>'typeSelectedName',
            'value'=>'$data->typeSelected->name',
            'filter'=> $this->widget('EchMultiselect', array(
                'model' => $model,
                'dropDownAttribute' => 'typeSelectedName',
                'dropDownHtmlOptions'=> array(
                     'style'=>'width:225px;',
                     'multiple'=>true,
           ),
          'data' => array('A'=>'A','B'=>'B','C'=>'C','Z'=>'Z','X'=>'X','K'=>'K','T'=>'T'),
           'options' => array(
                'header'=> Yii::t('EchMultiSelect.EchMultiSelect',''),
                'buttonWidth' => 80, 
                'position'=>array('my'=>'left bottom', 'at'=>'left top'),
                'ajaxRefresh' => true,  
                'multiselect'=>true,
                'filter'=>true,
           ),
         ),
       true // capture output; needed so the widget displays inside the grid
     ),
   ),
Model
$criteria=new CDbCriteria;
    $criteria->compare('id',$this->id);
    if(!empty($this->type)) {
       foreach($this->type as $v) {
             $criteria->compare('type', $v, false, 'OR');
                    }
            }
    $criteria->compare('sa_id',$this->sa_id,true);
...
i am using yii 1.1.13 and i can see this Cgridview:

                        
typeSelectedNamewhile in the model file for criteria you checktypeattribute.Better you add some options inside multiselect to invoke custom ajax for model filtering: upon returned data do update grid. This way multyselect will be working as the only filter option (no other options will be taken into account); though you might get form data thru
this.form.serialize()and make joined filtering.