"ACCESS DENIED" in user mode accessing event created by IoCreateNotificationEvent during DRIVERENTRY

hello all,
I use IoCreateSynchronizationEvent(…) in system process ( driverentry() time ). when I try to open this event in usermode using OpenEvent(…EVENT_ALL_ACCESS…) it fails with “ACCESS DENIED”. I tried ZwCreateEvent(…EVENT_ALL_ACCESS…). still no luck. I think it is something to do with security issue, i.e creating an event “before” logon and trying to access it after it. So how to make this scheme work?? should i try some flags like STANDARD_RIGHTS_ALL etc?

thanks & regds
alex