Exchange ActiveSync and iPhone: Messages stopped again

Client reports that ActiveSync has stopped working yet again...  checked PoolMon for Non-paged Pool and it's fine...

There's an event in the Application Log for ActiveSync - ID 3033.

Following this article:
http://support.microsoft.com/kb/905013/en-us

I checked the suggested registry key...

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MasSync\Parameters

And all four DWORDs are missing... I have set them to:

• MinHeartbeatInterval - Dword - Decimal 60 (seconds)
• MaxHeartbeatInterval - Dword - Decimal 2700 (seconds)
• HbiSampleSize - Dword - Decimal 200 (samples)
• HbiAlertThreshold - Dword - Decimal 480 (seconds)

It suggests changing the HTTP(S) timeout values on the router firewall but I can't find them... so I'm going to do a simple IISRESET and see if that resolves the problem.  Trouble is, an IISRESET might just resolve the issue, despite the new registry entries... so I can only warn the client that's a possibility... (when he returns)...

If that doesn't resolve the issue for now... back to the drawing board...