nopCommerce 1.4 product save issue [solved]

Hi,
we are running a shop with version 1.4. It's up for 1.5 year but since yesterday we are getting following error on product save:

[InvalidOperationException: Operation is not valid due to the current state of the object.]
   System.Web.HttpRequest.FillInFormCollection() +532
   System.Web.HttpRequest.get_Form() +84
   System.Web.HttpRequest.get_HasForm() +107
   System.Web.UI.Page.GetCollectionBasedOnMethod(Boolean dontReturnNull) +75
   System.Web.UI.Page.DeterminePostBackMode() +139
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +304

Any ideas what's wrong?
Thank you.

Here are some more details:
http://forums.aurigma.com/yaf_postst4868_Operation-is-not-valid-due-to-the-current-state-of-the-object.aspx

should be caused by:
http://technet.microsoft.com/en-us/security/bulletin/ms11-100

Now, how to fix it?

Nice, I have found a working solution, following is needed in web.config:

<appSettings>
  <add key="aspnet:MaxHttpCollectionKeys" value="5000" />
</appSettings>

Source with explanation:
http://arthicksdev.wordpress.com/2012/01/04/microsoft-security-bulletin-ms11-100-critical-issues-and-fixes/