Users facing erros in Opportunity

Hi, i am using crm online . Some users are getting the below error, users belongs to few business units are facing this error. They have sufficient priveleges to create the Opportunity and also this is happening only after the Upgrade from 2015 to update 1.

Unhandled Exception: System.ServiceModel.FaultException`1[[Microsoft.Xrm.Sdk.OrganizationServiceFault, Microsoft.Xrm.Sdk, Version=7.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35]]: Unexpected exception from plug-in (Execute): Sonoco.Plugin.Opportunity.PostCreate: System.Exception: The user Id(s) [85986e43-ffad-e311-825f-6c3be5a80f9c] is invalid.Detail:

<OrganizationServiceFault xmlns:i="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://schemas.microsoft.com/xrm/2011/Contracts">

<ErrorCode>-2147220956</ErrorCode>

<ErrorDetails xmlns:d2p1="http://schemas.datacontract.org/2004/07/System.Collections.Generic" />

<Message>Unexpected exception from plug-in (Execute): Sonoco.Plugin.Opportunity.PostCreate: System.Exception: The user Id(s) [85986e43-ffad-e311-825f-6c3be5a80f9c] is invalid.</Message>

< Timestamp>2015-10-19T20:26:47.2275469Z</Timestamp>

<InnerFault i:nil="true" />

<TraceText>

[Sonoco.Plugin.Opportunity: Sonoco.Plugin.Opportunity.PostCreate]

[766b9b7a-3575-e411-94c4-a45d36fd3164: Sonoco.Plugin.Opportunity.PostCreate: Create of opportunity]

</TraceText>

</OrganizationServiceFault>

Thanks in Advance.