BES Blackberry Router Service Problem

Hi Guys,

I have a BES Express 5.0.3.41 server with approx. 20 users, running on Windows 2008 R2.   The Blackberry Router service is generating critical errors every Sunday between approx 07.00 and 10.00.  The errors are all Event ID 10000 and are similar to this:

[SERVICE_RELAY_SESSION:S33885072:0x00A66078] Service transaction not found. SERVICESESSION_TAG=15369165

The problem seems to be delaying sending of emails from Blackberry devices for up to an hour during the time the errors are logged, but after a few hours the delay disappears and the BES MAGT log seems to confirm this.

The problem doesn't occur at any other time.

I've checked for any programs or tasks such as backups that might be running at the time but cannot identify anything.

Any ideas would be much appreciated.

Thanks