One of the users on my network is having an issue with his iPhone syncing via ActiveSync. Overall it's working, but every now and then he gets a "Synchronization with your iPhone failed for 3 items." I asked him to go into OWA and turn on the Mobile Phone logging. I looked through the logs and this is what stood out to me: SyncCommand_GenerateResponsesXmlNode_AddChange_Exception : Microsoft.Exchange.Data.Storage.PropertyErrorException: Property: [{00062008-0000-0000-c000-000000000046}:0x8501] ReminderMinutesBeforeStartInternal, PropertyErrorCode: NotFound, PropertyErrorDescription: . at Microsoft.Exchange.Data.Storage.PropertyBag.ThrowIfPropertyError(StorePropertyDefinition propertyDefinition, Object propertyValue) at Microsoft.Exchange.Data.Storage.StoreObject.GetProperty(PropertyDefinition propertyDefinition) at Microsoft.Exchange.Data.Storage.MeetingMessage.get_Item(PropertyDefinition propertyDefinition) at Microsoft.Exchange.AirSync.SchemaConverter.XSO.XsoMeetingRequestProperty.get_NestedData() at Microsoft.Exchange.AirSync.SchemaConverter.AirSync.AirSyncMeetingRequestProperty.InternalCopyFrom(IProperty srcProperty) at Microsoft.Exchange.AirSync.SchemaConverter.AirSync.AirSyncProperty.CopyFrom(IProperty srcProperty) at Microsoft.Exchange.AirSync.SchemaConverter.AirSync.AirSyncDataObject.CopyFrom(IProperty srcRootProperty) at Microsoft.Exchange.AirSync.SyncCollection.ConvertServerToClientObject(ISyncItem syncItem, XmlNode airSyncParentNode, SyncOperation changeObject) at Microsoft.Exchange.AirSync.SyncCollection.GenerateCommandsXmlNode(XmlDocument xmlResponse, IAirSyncVersionFactory versionFactory, String deviceType, ProtocolLogger protocolLogger, MailboxLogger mailboxLogger) Does anyone have any idea what might cause this? We have 4 iPhone users connected to our Exchange via ActiveSync. Right now, this seems to be the only user experiencing this issue. I'd appreciate any help anyone can provide. Thanks.