沙盒代码执行请求被拒绝，因为沙盒代码主机服务太忙，无法处理请求。

http://msdn.microsoft.com/en-us/library/gg615462.aspx

$uc = [Microsoft.SharePoint.Administration.SPUserCodeService]::Local
$uc.WorkerProcessExecutionTimeout = 5000
$uc.Update()

$tier = $uc.Tiers[""]   # default Tier has no Name
$tier.MaximumWorkerProcesses = 2    # number of CPU Cores + 1
$tier.Update()

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

http://www.sharepointblogs.be/blogs/vandest/archive/2011/12/07/the-sandbox-is-too-busy-to-handle-the-request.aspx