SharePoint Foundation Sandboxed Code Service - Unable to activate worker process proxy object within the worker process

Issue:

On a vanilla installation, the sandboxed code service (e.g. SPUCHostService.exe) is started; however, SPUCWorkerProcessProxy.exe and subsequently SPUCWorkerProcess.exe fails to start.

Resolution/Workarounds attempted:

1. Attempted 2 different Load balancing settings – local and remote (i.e. affinity)
2. Ensured local computer policy on server for ‘RPC Endpoint Mapper Client Authentication’ and ‘Restrictions for Unauthenticated RPC clients’ is disabled.
3. Ensured following key in registry is set properly - HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows NT\RPC
4. Attempted to bypass SharePoint’s check for certificate revocations at crl.microsoft.com
5. Ensured the service account is added to the respective groups (e.g. Performance Log Users, Performance Monitor Users, IIS_IUSRS, WSS_ADMIN_WPG, WSS_WPG)
6. Increased limit of ‘AbnormalProcessTerminationCount’ of SPUserCodeService via Powershell

We have tried all possible workarounds from the following MSDN reference: 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

ULS:

02/21/2014 05:24:50.64  SPUCHostService.exe (0x0230)  0x0F74  SharePoint Foundation Sandboxed Code Service              fe8a                Medium               -  - Unable to activate worker process proxy object within the worker process: ipc://38432b45-2f32-4926-ade2-ef53ae1cd501:7000  

02/21/2014 05:24:50.64  SPUCHostService.exe (0x0230)  0x0F74  SharePoint Foundation Sandboxed Code Service              fe8c                Medium               -  - Error activating the worker process manager instance within the worker process. - Inner Exception: System.InvalidOperationException: Unable to activate worker process proxy object within the worker process: ipc://38432b45-2f32-4926-ade2-ef53ae1cd501:7000     at Microsoft.SharePoint.UserCode.SPUserCodeWorkerProcess.CreateWorkerProcessProxies()    

02/21/2014 05:24:50.64  SPUCHostService.exe (0x0230)  0x0F74  SharePoint Foundation Sandboxed Code Service              ei0t                Medium               - Process creation/initialization threw an exception. Stopping this process. "ipc://38432b45-2f32-4926-ade2-ef53ae1cd501:7000"

02/21/2014 05:24:50.65  SPUCHostService.exe (0x0230)  0x0F74  SharePoint Foundation Sandboxed Code Service              fe87                Medium               -  - Error activating the worker process manager instance within the worker process. - Starting worker process threw - Inner Exception: System.InvalidOperationException: Unable to activate worker process proxy object within the worker process: ipc://38432b45-2f32-4926-ade2-ef53ae1cd501:7000     at Microsoft.SharePoint.UserCode.SPUserCodeWorkerProcess.CreateWorkerProcessProxies()   

Any other insights on how I can troubleshoot the issue described?

Thanks in advance!