I'm trying to edit a content page and inserting an Image there - done that plenty times before.

Now the image gets uploaded to the media folder when clicking save, but the error written further down in this msg appears.

Someone familiar with this problem, or where to look for a resolution? The site is running fine in production, so I don't wish to upgrade the umbraco if I can avoid that.

umbraco v 3.0.5 (Assembly version: 1.0.3050.25839)

ASP.NET 2.0 Classic App Pool

IIS 7, Windows Server 2008 

Server Error in '/' Application.
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Object reference not set to an instance of an object.
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.NullReferenceException: Object reference not set to an instance of an object.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.
 

Stack Trace:

[NullReferenceException: Object reference not set to an instance of an object.]
   umbraco.dialogs.uploadImage.Page_Load(Object sender, EventArgs e) +1603
   System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +14
   System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +35
   System.Web.UI.Control.OnLoad(EventArgs e) +99
   umbraco.BasePages.BasePage.OnLoad(EventArgs e) +44
   System.Web.UI.Control.LoadRecursive() +50
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +627

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Version Information: Microsoft .NET Framework Version:2.0.50727.4206; ASP.NET Version:2.0.50727.4209