Is it possible to parse a local xml file when using ST and phonegap on Android (ICS)?

I tried it with a store
Code:
var mystore = new Ext.data.Store({
    model: 'mymodel',
    proxy: {
        type: 'ajax',
        url : 'myfile.xml',
        reader: {
            type: 'xml',
            root: 'myroot',
            record: 'myrecord'
        }
    }
});

[...]
mystore.load({
      scope   : this,
      callback: function(records, operation, success) {
        console.log('success: '+success);
      }
});
but all I got was an Uncaught TypeError (Cannot read property 'length' of undefined)
the I tried Ajax.request:
Code:
  Ext.Ajax.request({
    url: 'myfile.xml',
        success: function() {
console.log('sucess!!!');
        },
        failure: function() {
console.log('failure!!!');
        }
      })
I tried it with a different url:
Code:
url: 'file:///android_asset/www/myfile.xml'
but I had no success.

Did anyone have the same problem and solved it somehow?

//edit: On my Android 2.3 device I can use the store + xmlReader without problems, but on 4.0 it just doesnt work ?!?

//edit2: I tried to put all my js files into one combined js -> still no success

errors in logcat: SqliteDatabaseCpp: sqlite returned: error code = 14, msg = cannot open file at line [,,,], db=data/data/de.my.app/databases/webview.db
chromium: Uknown chromium error: -6
PhoneGapLog: file:///android_asset/www/app/combined.js Line 1 : Uncaught TypeError: Cannot read property 'length' of undefined