Error While Search (Unknown Error / Object reference not set to an instance of an object)

Yesterday i started a new SharePoint project; so after setting up my MOSS farm with proper configuration for SSP and search settings i tried to search a word (opening IE from the server itself) and it worked perfectly :).

Today i opened my machine, navigated to the portal using the FQN (Fully qualified name hostName.domainName.com), tried to search and the following error popped up : Unknown error. also i modified the web.config to call the Stacktrace and turn off customError, then error changed to:

Object reference not set to an instance of an object.   at Microsoft.Office.Server.Search.WebControls.CoreResultsWebPart.OnLoad(EventArgs e)
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

So the reason for the error was simply because i am using the FQN (which is not the hostname as understandable by MOSS), so i added the machine name to the hosts file (because the DNS only resolves FQN) and it worked.