Problem Module/datagrid, one time with data, one time is null

Question

Hello All
thanks for this discussion place, i have a problem in Flash Builder 4.6 (sdk 4.6.0), construct an application who connect to DB, for now, the CRUD works fine with flex service,
i have a problem with a datagrid, one time it's worked fine, and another time my obj is null, i cannot understand why.. the fact it's work one time trouble me.. and i have no error in console..
the target, is to edit a row of datagrid in popup, it's work as you stay in the ModuleClient, but when i launch another Module and come back to ModuleClient, the edit datagrid doesn't work anymore
i try to put the process here, as the app is large: (say to me if you want more code, i will try to isolate some pieces)
- click in ModuleMenu and load ModuleClient in ModuleContent
- dataGrid populate with ArrayCollection
- double click row in dataGrid (dataGrid_doubleClickHandler(event:MouseEvent))
- dataGridClients.selectedItem contains effective data
- push data to ValueObject (ClientObj) already defined in flex services/connected to DB
          var ClientDataGrid:ClientObj = dataGridClients.selectedItem as ClientObj;
- push data ClientDataGrid to Popup
          in Popup: <valueObjects:ClientObj id="clientObj"/>
- works fine
if i select another Module in ModuleMenu, and later relaunch ModuleClient
- dataGrid populate with ArrayCollection
- double click row in dataGrid
- dataGridClients.selectedItem contains effective data
- push data to ValueObject (ClientObj) already defined in flex services/connected to DB
          var ClientDataGrid:ClientObj = dataGridClients.selectedItem as ClientObj;
- ClientDataGrid is null
- cannot push data ClientDataGrid to Popup as ClientDataGrid is null
- doesn’t work
<s:DataGrid id="dataGridClients" left="0" right="230" top="66" bottom="10"
creationComplete="dataGrid_creationCompleteHandler(event)"
dataProvider="{clientListeSimpleResult.lastResult}"
doubleClick="dataGrid_doubleClickHandler(event)" doubleClickEnabled="true"
alternatingRowColors="[#FFFFFF, #f4f3f2]">
Thanks in advance for any advices/ideas
i think i make misunderstood of something, im not a flex/flash as3 coder
so any help would be greatly appreciated
best regards anyway

Answer 1

thanks Alex for your link, i read it carrefully, i have to study some thing imo
but, i don't find solution for now, otherwise, i found a strangely similar problem here : it's seem to be the same problem as i have :
https://issues.apache.org/jira/browse/FLEX-18680 [After Module reload dataGrid.selectedItem as MyClass NOT WORKING]
do you think i encounter a bug?
(i will try to isolate some code to test more)
thanks again for advices/ideas