When adding a page to several of my portals (some do work fine), i receive the following error:

System.NullReferenceException was caught 
  Message="Object reference is not set to an instance of an object."
  Source="DotNetNuke"
  StackTrace:
       bij DotNetNuke.Entities.Tabs.TabController.AddAllTabsModules(TabInfo objTab) in C:\Coding\DNN_source\Library\Entities\Tabs\TabController.vb:regel 60
       bij DotNetNuke.Entities.Tabs.TabController.AddTabInternal(TabInfo objTab, Boolean includeAllTabsModules) in C:\Coding\DNN_source\Library\Entities\Tabs\TabController.vb:line 99
       bij DotNetNuke.Entities.Tabs.TabController.AddTab(TabInfo objTab, Boolean includeAllTabsModules) in C:\Coding\DNN_source\Library\Entities\Tabs\TabController.vb:line 365
       bij DotNetNuke.Entities.Tabs.TabController.AddTab(TabInfo objTab) in C:\Coding\DNN_source\Library\Entities\Tabs\TabController.vb:regel 348
       bij DotNetNuke.Modules.Admin.Tabs.ManageTabs.SaveTabData(String strAction) in C:\Coding\DotNetNuke\DesktopModules\Admin\Tabs\ManageTabs.ascx.vb:line 560
       bij DotNetNuke.Modules.Admin.Tabs.ManageTabs.cmdUpdate_Click(Object Sender, EventArgs e) in C:\Coding\DotNetNuke\DesktopModules\Admin\Tabs\ManageTabs.ascx.vb:line 915
  InnerException:

I apologize for the partly dutch stacktrace, i used the dnn source package to find out where the error occurres, The errors occur since my admin tabs were deleted from the tabs table by dnn no clue why that happend bug?  Tabmodules and modules are still intact. I just restored all admin tabs, this didn't solve anything.