Have you experienced “Error: “The sandboxed code execution request was refused because the Sandboxed Code Host Service was too busy to handle the request” when you try to activate your sandbox solution and Microsoft SharePoint Foundation Sandboxed Code Service is running OK on your server? Well.. this is what happened to me today. Check below post http://blogs.msdn.com/b/sharepointdev/archive/2011/02/08/error-the-sandboxed-code-execution-request-was-refused-because-the-sandboxed-code-host-service-was-too-busy-to-handle-the-request.aspx. This is actually caused by incorrect registry key and below is the workaround that works for me:
1. On the server, click Start | Administrative Tools | Services.
2. On the Services dialog, scroll to SharePoint 2010 User Code Host.
3. Note the full user name in the Log On As column. You will need this information later.
4. Open SharePoint Management Shell.
5. Enter the following at the command prompt, including all punctuation.
(Get-SPManagedAccount –Identity “username”).Sid.Value
Replace username with the name you obtained in step 3. E.g., CorpDomain\FarmAdmin
This will return the user’s SID (Security ID), which you will use in a later step.
6. Open the registry editor and navigate to:
HKEY_USERS\SID you obtained earlier\SOFTWARE\Microsoft\Windows\CurrentVersion\WinTrust\Trust Providers\SoftwarePublishing
7. Be sure the State key value is set to 0x00023e00.
8. Restart the sandboxed host service on all servers on which it is to run. It cannot hurt to do an iisreset as well.
