ExtJs 4.2.0.663 using Searchfield results in the exception "PageMap requests a range that it does not have",

since ExtJS 4.2 has an error in using filters on a buffered grid (infinite grid), I rewrote my code and now I just use a simple search field to allow the user to search the entire grid for data. as long as something is found, it works fine, but if nothing is found, then ext fails, the page map requested a range that it doesn’t have.

my javascript "includes"

<script type="text/javascript" src="/js/ext-4.2.0.663/examples/ux/grid/filter/Filter.js"></script>
<script type="text/javascript" src="/js/ext-4.2.0.663/examples/ux/grid/filter/BooleanFilter.js"></script>
<script type="text/javascript" src="/js/ext-4.2.0.663/examples/ux/grid/filter/DateFilter.js"></script>
<script type="text/javascript" src="/js/ext-4.2.0.663/examples/ux/grid/filter/ListFilter.js"></script>
<script type="text/javascript" src="/js/ext-4.2.0.663/examples/ux/grid/filter/NumericFilter.js"></script>
<script type="text/javascript" src="/js/ext-4.2.0.663/examples/ux/grid/filter/StringFilter.js"></script>


<script type="text/javascript" src="/js/ext-4.2.0.663/examples/ux/grid/menu/ListMenu.js"></script>
<script type="text/javascript" src="/js/ext-4.2.0.663/examples/ux/grid/menu/RangeMenu.js"></script>


<script type="text/javascript" src="/js/ext-4.2.0.663/examples/ux/grid/FiltersFeature.js"></script>
<script type="text/javascript" src="/js/ext-4.2.0.663/examples/ux/grid/TransformGrid.js"></script>


<script type="text/javascript" src="/ASDB4/js/ext-4.2.0.663/examples/ux/form/SearchField.js"></script>

my shop:

this._store = Ext.create('Ext.data.Store', {
     storeId: 'ActivityLogStore',
     model: 'ActivityLogModel',
     remoteGroup: true,
     autoDestroy: true,
     buffered: true,
     remoteSort: true,
     leadingBufferZone: 300,
     pageSize: 100,
     autoLoad: true,
     proxy: {
         type: 'ajax',
         url: '~myurl~',
         reader: {
             root: 'data[0].sActivityLogsArr',
             totalProperty: 'data[0].totalcount'
         },
         simpleSortMode: true,
         simpleGroupMode: true,
         groupParam: 'sort',
         groupDirectionParam: 'dir',
         filterParam: 'searchString',
         encodeFilters: function (filters) {
             return filters[0].value;
         }
     },
     listeners: {


         // This particular service cannot sort on more than one field, so if grouped, disable sorting
         groupchange: function (store, groupers) {
             var sortable = !store.isGrouped(),
                 headers = grid.headerCt.getVisibleGridColumns(),
                 i, len = headers.length;


             for (i = 0; i < len; i++) {
                 headers[i].sortable = (headers[i].sortable !== undefined) ? headers[i].sortable : sortable;
             }
         },


         beforeload: function () {
             // remove any selections - otherwise store loading crashes (another bug in extjs ...?)
             Ext.getCmp('activityLogmanagergrid').getSelectionModel().clearSelections();
         },


         // This particular service cannot sort on more than one field, so if grouped, disable sorting
         beforeprefetch: function (store, operation) {
             if (operation.groupers && operation.groupers.length) {
                 delete operation.sorters;
             }
         },


         load: function () {
             Ext.getCmp('activityLogmanagergrid').verticalScroller.scrollTo(0);
         }
     }
 });  

my search box located on the toolbar:

 this._moduleToolbar = {
     xtype: 'toolbar',
     itemId: 'activityLogmanagerToolbar',
     items: [{
             iconCls: 'icon-arrow_refresh',
             text: '@menu_reload@',
             itemId: 'btnReload',
             scope: this,
             handler: function () {
                 // reset list display to top to avoid corrupted display
                 Ext.getCmp('activityLogmanagergrid').store.load();
             }
         }, {
             iconCls: 'icon-cross',
             text: '@menu_deleteAllActivityLog@',
             itemId: 'btnDeleteAll',
             scope: this,
             handler: this.DeleteAllActivityLog
         }, '->', {
             width: 300,
             fieldLabel: 'Search',
             labelWidth: 50,
             xtype: 'searchfield',
             store: scope._store
         }
     ]
 }; 

please, help...