Errore server forum aessenet

Server Error in '/' Application.
Index was outside the bounds of the array.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.IndexOutOfRangeException: Index was outside the bounds of the array.

Source Error:

Line 170: */
Line 171:
Line 172: UtenteOnline_PageView(UtentiOnlineOperazioniEnum.Forum, IDFORUM);
Line 173:
Line 174:


Source File: c:\Inetpub\wwwffz3\forum.aspx.cs Line: 172

Stack Trace:

[IndexOutOfRangeException: Index was outside the bounds of the array.]
System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add) +681
System.Collections.Generic.Dictionary`2.Add(TKey key, TValue value) +19
ffz.BLL.UtentiOnlineManager.SessionEnter(UtentiOnline UO, SessionFFZ Sessione, UtenteOnline uoline) in C:\Webapps\FreeForumZone\3.0\www\Progetto\FreeForumZone3\ffz\BLL\UtentiOnlineManager.cs:424
ffz.BLL.UtentiOnlineManager.EseguiPageview(Int32 IDCOMUNITA, UtentiOnline UO, SessionFFZ Sessione, Utente ut, UtenteComunita utc, UtentiOnlineOperazioniEnum Operazione, Int32 ID_EXT) in C:\Webapps\FreeForumZone\3.0\www\Progetto\FreeForumZone3\ffz\BLL\UtentiOnlineManager.cs:350
System.Web.UI.FPage.UtenteOnline_PageView(UtentiOnlineOperazioniEnum operazione, Int32 ID_EXT) in C:\Webapps\FreeForumZone\3.0\www\Progetto\FreeForumZone3\ffz\System.Web.UI\FPage.cs:1494
forum.Page_Load(Object sender, EventArgs e) in c:\Inetpub\wwwffz3\forum.aspx.cs:172
System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +25
System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +58
System.Web.UI.Control.OnLoad(EventArgs e) +127
System.Web.UI.Control.LoadRecursive() +101
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2588


Version Information: Microsoft .NET Framework Version:2.0.50727.832; ASP.NET Version:2.0.50727.832


ultimamente mi appare spesso mi dite che significa?