Sharepoint 2010无法以IIS池标识帐户运行提升代码

我更改了Sharepoint 2010 web应用程序的IIS池身份服务帐户，从而取代了默认的"Network service "帐户(使用Sharepoint Administrator)。池服务帐户权限现在由MS在"应用程序池帐户"部分中记录:http://technet.microsoft.com/en-us/library/cc678863%28v=office.14%29.aspx

我的功能中的提升代码在尝试激活其他站点功能时失败，有以下例外:

创建站点时出现异常:对此进行安全验证页面无效。在Web浏览器中单击Back，刷新页面，然后

堆栈跟踪:

at Microsoft.SharePoint.SPGlobal.HandleComException(COMException comEx)    
 at Microsoft.SharePoint.Library.SPRequest.ValidateFormDigest(String bstrUrl, String bstrListName)    
 at Microsoft.SharePoint.SPWeb.ValidateFormDigest()    
 at Microsoft.SharePoint.SPSecurity.ValidateSecurityOnOperation(SPOperationCode code, SPSecurableObject obj)    
 at Microsoft.SharePoint.SPFeature.AddRowToFeaturesTable(SPFeaturePropertyCollection props, SPSite site, SPWeb web, Boolean fForce)    
 at Microsoft.SharePoint.SPFeature.Activate(SPSite siteParent, SPWeb webParent, SPFeaturePropertyCollection props, SPFeatureActivateFlags activateFlags, Boolean fForce)    
 at Microsoft.SharePoint.SPFeatureCollection.AddInternal(SPFeatureDefinition featdef, Version version, SPFeaturePropertyCollection properties, SPFeatureActivateFlags activateFlags, Boolean force, Boolean fMarkOnly)    
 at Microsoft.SharePoint.SPFeatureCollection.AddInternalWithName(Guid featureId, String featureName, Version version, SPFeaturePropertyCollection properties, SPFeatureActivateFlags activateFlags, Boolean force, Boolean fMarkOnly, SPFeatureDefinitionScope featdefScope)    
 at Microsoft.SharePoint.SPFeatureCollection.Add(Guid featureId)  

池标识用户还需要哪些权限才能正常运行提升代码?如果我将池身份设置为我的农场帐户(如owtimer服务)是否存在安全风险?(如果是，为什么?)