haven't tried on 4.0.5.. have 4.0.3 and 4.0.6

try this little change.. (the 1st and last lines are the same, section in the middle changes a tiny bit )

            IItemQuery query = IItemQuery.FACTORY.newInstance(queryModel);
            // objects of build definition type, shouldn't be needed
            IPredicate isBuildDefType = queryModel._isTypeOf(IBuildDefinition.ITEM_TYPE);
            // allocate space for the parameter
            IItemHandleInputArg[] itemHandleArgs = new IItemHandleInputArg[]{query.newItemHandleArg()};
            // the query filter
            IPredicate filter = ((BuildDefinitionQueryModel) queryModel).processArea()._in(itemHandleArgs);
            // set the combined filter
            query.filter(filter._and(isBuildDefType));
            // no parameters required

try this one I just wrote
private static ArrayList<IBuildDefinition> getBuildDefinitionsforProjectArea(IProjectAreaHandle iprja)
    {
        Boolean allProperties = true;
        // allocate space for results
        ArrayList<IBuildDefinition> allbe = new ArrayList<IBuildDefinition>();
        ITeamRepository repo= (ITeamRepository)iprja.getOrigin();
        // get the data interface
        ITeamBuildClient buildClient = (ITeamBuildClient) repo.getClientLibrary(ITeamBuildClient.class);

        try
        {
            IBuildDefinitionQueryModel queryModel = IBuildDefinitionQueryModel.ROOT;
            // create a query for build engines
            IItemQuery query = IItemQuery.FACTORY.newInstance(queryModel);
            // allocate space for the parameter
            IItemHandleInputArg[] itemHandleArgs = new IItemHandleInputArg[]{query.newItemHandleArg()};
            // the query filter
            IPredicate filter = ((BuildDefinitionQueryModel) queryModel).processArea()._in(itemHandleArgs);
            // set the combined filter
            query.filter(filter);
            // no parameters required
            IItemQueryPage queryPage = buildClient.queryItems(query,
            // com.ibm.team.repository.common.service.IQueryService.EMPTY_PARAMETERS,
                    new Object[]{iprja}, IQueryService.ITEM_QUERY_MAX_PAGE_SIZE, null);

            // if there are build definitions defined

            if (queryPage.getResultSize() != 0)
            {
                while (queryPage != null)
                {
                    IFetchResult fetchResult = null;
                    if (allProperties == true)
                    {
                        fetchResult = repo.itemManager().fetchCompleteItemsPermissionAware(queryPage.getItemHandles(),
                                IItemManager.DEFAULT, null);
                    }
                    else
                    {
                        final String[] all_properties = new String[]
                        { IBuildEngine.PROPERTY_ACTIVE, IBuildEngine.PROPERTY_BUILD_ENGINE_ACTIVITY,
                                IBuildEngine.PROPERTY_DESCRIPTION, IBuildEngine.PROPERTY_ENGINE_CONTACT_INTERVAL,
                                IBuildEngine.PROPERTY_ID, IBuildEngine.PROPERTY_PROCESS_AREA,
                                IBuildEngine.PROPERTY_SUPPORTED_BUILD_DEFINITIONS,
                                IBuildEngine.PROPERTY_SUPPORTS_CANCELLATION, IBuildEngine.PROPERTY_USE_TEAM_SCHEDULER,
                                IBuildEngine.PROPERTY_PROPERTIES, IBuildEngine.PROPERTY_CONFIGURATION_ELEMENTS };
                       
                        fetchResult = repo.itemManager().fetchPartialItemsPermissionAware(queryPage.getItemHandles(),
                                IItemManager.DEFAULT, Arrays.asList(all_properties), null);
                    }

                    // add these to the list
                    allbe.addAll(fetchResult.getRetrievedItems());

                    if (queryPage.hasNext())
                    {
                        queryPage = (IItemQueryPage) buildClient.fetchPage(queryPage.getToken(),
                                queryPage.getNextStartPosition(), queryPage.getSize(), null);
                    }
                    else
                    {
                        queryPage = null;
                    }
                }
            }
        }
        catch (Exception ex)
        {
            System.out.println("build exception=" + ex.getMessage());
        }
        return allbe;
    }