Recently a customer of mine is experiencing problems with their production environment.

The SharePoint 2010 farm consist of a single WFE server with several site collections and is installed on Windows server 2008 R2 SP1. The notables are:

  • Intranet
  • Public Website

Once they start using the publishing function from intranet to the public website a few times, they start having issues with creating certain kind of pages.

Starting from the occurrence of the error. About half of the type of pages / locations give the below listed error.

Loading this assembly would produce a different grant set from other instances. (Exception from HRESULT: 0x80131401)

An IIS reset does solve the issue temporary until a few new pages and publishing's later.

I found a few posts online relating this issue to Microsoft updates and hotfixes. At which an new update / hotfix resolves the problem.

Sadly this is not the case for this particular scenario.

Does anyone know possible causes for this problem and resolutions?

Please request any information you still need if the above description was incomplete.


In a hope to resolve the issue the following actions have been defined. I will update the results of these actions:

  • Installing the newest Windows updates and hotfixes (action completed, bug not resolved)
  • Installing hotfix: http://www.microsoft.com/en-us/download/details.aspx?id=28948 (action canceled, not applicable for the environment)
  • Re-building and deploying all custom solutions after updating the development environment
  • Resetting all application pool users passwords
  • 1
    what sharepoint version you are using? did you apply the hot fix? also did you check the trust level in the web.config...make it full.
    – Waqas Sarwar MVP
    Commented Oct 18, 2014 at 6:40
  • Hello Waqas, sorry I though I included the version in the matetags. SharePoint 2010. I applied all current updates and hotfixes for Windows 2008 R2. Commented Oct 19, 2014 at 16:29
  • Were you able to collect relevant ULS logs and pinpoint the failing assembly? There might be unwanted interop calls in domain-neutral assemblies or something like that - either in Microsoft or third-party assemblies. See support.microsoft.com/kb/2282372 Commented Nov 3, 2014 at 20:59
  • Faced the same problem on SP2010 farm when trying to open list form with Infopath web part. IIS reset helps to solve the problem, at least temporarily. Commented Nov 17, 2015 at 10:18

1 Answer 1


Check the value of the legacyCasModel attribute of the trust element in the SharePoint web.config:

<trust level="Full" originUrl="" legacyCasModel="true" />

If legacyCasModel is set to "true," then change it to "false". Save the web.config file

  • This is security wise not a good solution. The correct solution is to add a DWORD value named LoaderOptimization with a value 1 under the registry key HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFramework. Has something to do with the way CAS is handled by the .NET 4 framework. Commented Dec 12, 2017 at 10:17
  • @LarsFastrup: do you have a link that details what you said ?
    – Steve B
    Commented Apr 19, 2021 at 17:26

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