Any help will be appriciated...

I have installed several times DNN 4.0, 4.01 and 4.02 from scratch on my hosting provider and when I am trying to submit something on any of the native or 3rd party modules SOMETIMES I get a Object reference not set to an instance of an object

A more detailed error to one of the modules (newsletters):

AssemblyVersion: 04.00.02
Method: FreeTextBoxControls.Support.ResourceManager.LoadResource
FileName:
FileLineNumber: 0
FileColumnNumber: 0
PortalID: 0
PortalName: Lefteris Karafilis - Personal web site
UserID: 1
UserName: host
ActiveTabID: 45
ActiveTabName: Newsletters
AbsoluteURL: /Default.aspx
AbsoluteURLReferrer:
ExceptionGUID: ecea150d-433f-45d0-9f35-d00db92347a3
DefaultDataProvider: DotNetNuke.Data.SqlDataProvider, DotNetNuke.SqlDataProvider
InnerException: Unhandled Error:
Message: System.Exception: Unhandled Error: ---> DotNetNuke.Services.Exceptions.PageLoadException: Object reference not set to an instance of an object. ---> System.NullReferenceException: Object reference not set to an instance of an object. at FreeTextBoxControls.Support.ResourceManager.LoadResource(Hashtable target, String language, String cacheKey) at FreeTextBoxControls.Support.ResourceManager.GetResources() at FreeTextBoxControls.Support.ResourceManager.GetString(String name) at FreeTextBoxControls.Support.Helper.PopulateDefaultDropDownList(ToolbarDropDownList toolbarDropDownList, FreeTextBox freeTextBox, ResourceManager resourceManager) at FreeTextBoxControls.FreeTextBox.OnPreRender(EventArgs e) at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) --- End of inner exception stack trace --- at DotNetNuke.Services.Exceptions.Exceptions.ProcessPageLoadException(Exception exc, String URL) at DotNetNuke.Framework.PageBase.Page_Error(Object Source, EventArgs e) at System.Web.UI.TemplateControl.OnError(EventArgs e) at System.Web.UI.Page.HandleError(Exception e) at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) at System.Web.UI.Page.ProcessRequest(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) at System.Web.UI.Page.ProcessRequest() at System.Web.UI.Page.ProcessRequestWithNoAssert(HttpContext context) at System.Web.UI.Page.ProcessRequest(HttpContext context) at ASP.default_aspx.ProcessRequest(HttpContext context) at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) --- End of inner exception stack trace ---
StackTrace:
Source:
Server Name: S64996

I finally found an answer to another post. I had to create an el-GR.xml (greek localization) file and to add this reference to languages.xml file.

Thanks very much for any help