Error while evaluating a workflow - Invalid Operation when not in update mode

 Hi,

We are getting the Invalid Operation error whenever we try to save a sub opportunity. We have a workflow that updated the Forecast checkbox based on certain conditions. This workflow works fine if we save a parent opportunity but throws this error when creating a sub opportunity, although it saves the record but doesn't check the checkbox.

Following are the workflow details :

Record Type : Opportunity

Trigger Event : When New Record Saved

Workflow Rule Condition : (InStr("Confirmed,Bid/Proposal Preparation,Decision Pending,Decision/ALB,No Bid/Proposal,Cancelled/Dead,Closed/Lost,Awarded,Closed/Won",[<SalesStage>])>0) AND ([<OpportunityType>]<>LookupValue("OCCAM_OPPTY_SALES_TYPE", "Contract Sub Opportunity")) AND ExcludeChannel("Import")