I am definately getting closer, I have added the Apex.AddMessage() function and the msg is still not displaying on the page.  I was thought theissue was a little more strait forward so I didnt include code, but I have inclded the code to assist with my explanation.

Custom Controller:

public class ProdCase {
	private final Opportunity o;
	
	
	public ProdCase(ApexPages.StandardController stdController) {
		this.o = (Opportunity)stdController.getRecord();
	}
	//For testability
	public ProdCase(Opportunity o) {
		this.o = o;
	}
	
//capture the opportunity id from the button
		public PageReference prodDetails(){
			String theID = ApexPages.currentPage().getParameters().get('id');
			if (theID == null){
				return null;
			}
			return prodDetails(theID);
		}
		
		 public PageReference prodDetails(String theID){
		 
			

//Build Oportunity Line Item List object with results from the matching records of the query
 			List<OpportunityLineItem> lin = [Select 
			o.UnitPrice,
			o.TotalPrice,
			o.ListPrice,
			o.Id,
			o.Opportunity.Pricebook2Id,
			o.PricebookEntryId,
			o.ServiceDate,
			o.Quantity,
			o.Description,
		    o.Transmission_Mode__c,
			o.Opportunity.Name,
			o.Opportunity.Type,
			o.Opportunity.Estimated_Implementation_Date__c,
			o.Opportunity.Opportunity_States__c,
			o.Opportunity.Implementation_Contac__c, 
			o.Opportunity.Implementation_Program__c
			From OpportunityLineItem o where o.OpportunityId =:theID and o.Implementation_Validation__c != true];	
			  //List<OpportunityLineItem> lin = [Select(Select UnitPrice, TotalPrice, 
			  //Quantity, ListPrice, Id From OpportunityLineItem WHERE Implementation_Validation__c != true)o.Name from Opportunity o where o.id =:theID] ;
			  
			  if (o.Implementation_Contac__c == null){
			 	ApexPages.Message myMsg = new ApexPages.Message(ApexPages.Severity.CONFIRM, 'The Implementation Contact has not been assigned, please correct and resubmit!');
			 	ApexPages.addMessage(myMsg);
			  	return ApexPages.currentPage(); 
			 }

//Build 
			list<Case> ToInsert = new list<Case>();
 				for(Integer I = 0; I < lin.size(); I++){
 	
 					//create the case object 
 					Case cas = new Case();

/*
Determine if the Opportuntiy is a Submitter, Vendor, or Receiver Opportuntiy and create the
correct case record type.
*/ 
	String oliID = lin[I].PricebookEntryId;
	List<PriceBookEntry> prd = [Select p.Product2Id from PricebookEntry p where Id =:oliID ];
	
	for(Integer ic = 0; ic < prd.size(); ic++){
		cas.Related_Products__c=prd[ic].Product2Id;
	
    }
	if(lin[I].Opportunity.Type == ('Submitter')){		
 		 cas.RecordTypeId='012600000004vNEAAY';
 		//Owner equals Ann Shelton
 		cas.OwnerId='00560000000lh2zAAA';	
 	}else if(lin[I].Opportunity.Type ==('Vendor')){	
 		cas.RecordTypeId='012600000004vacAAA';
 		//Owner equals Ann Shelton
 		cas.OwnerId='00560000000lh2zAAA';	
 	}else {	
 		cas.RecordTypeId='012600000004vN9AAI';
 		//Owner equals Cyn Criss
 		cas.OwnerId='00560000000lfXlAAI';		
 	}
 
    cas.Implementation_Name__c=lin[I].Opportunity.Name;
    cas.Status='Business Development';
    cas.Projected_Transactions__c=lin[I].Quantity;
    cas.States__c=lin[I].Opportunity.Opportunity_States__c;
    cas.ContactId=lin[I].Opportunity.Implementation_Contac__c;
	cas.Description=lin[I].Description;
	cas.Subject=lin[I].Opportunity.Name;
	cas.Implementation_Program__c=lin[I].Opportunity.Implementation_Program__c;
	
	//Sandbox
	//cas.Opportunity_Link__c='tapp0.salesforce.com/'+lin[I].OpportunityId;
	
	//Prd
	cas.Opportunity_Link__c='na4.salesforce.com/'+lin[I].OpportunityId;
	cas.Estimated_Implementation_Date__c=lin[I].Opportunity.Estimated_Implementation_Date__c;
	cas.Estimated_Live_Date__c=lin[I].ServiceDate;
//	cas.Related_Products__c=prd[ic].Product2Id;
	

//Sets the validation field true so that you can not submit a line item case more than once.					
    lin[I].Implementation_Validation__c = true;
    
//Insert the cas object into the ToInsert list.    
    ToInsert.add(cas);
    
  }
// Inserts all the objects within the ToInsert list 
  insert ToInsert;
  update lin;
  
  	PageReference pageRef = new PageReference('/' + theId);
	pageRef.setRedirect(true);
	return pageRef;
	}
}

VF Page:

<apex:page standardcontroller="Opportunity" extensions="ProdCase" action="{!prodDetails}">
    <apex:sectionHeader title="Oportunity Case Mesages"/>
  <apex:pageBlock >
  <apex:pageBlockSection >
  <apex:Form >
      <apex:pageMessages ></apex:pageMessages>
  </apex:Form>
  </apex:pageblockSection>
  </apex:pageBlock>
</apex:page>

When I run the code I get the following,

"

Visualforce Error

Help for this Page

System.SObjectException: SObject row was retrieved via SOQL without querying the requested field: Opportunity.Implementation_Contac__c
Class.ProdCase.prodDetails: line 48, column 31 Class.ProdCase.prodDetails: line 19, column 32 External entry point

"