Okay, can you help me find the bug?  

Here's my VF Page:

<apex:page standardController="Opportunity" extensions="newTransactionController" action="{!autoRun}">
  <apex:sectionHeader title="Creating New Transaction Record"/>
  <apex:outputPanel >
      <p><strong><span style="color:red">Could Not Process Check</span></strong></p>
  </apex:outputPanel>

</apex:page>

Here's my controller:

public class newTransactionController {
 
    // Constructor - this only really matters if the autoRun function doesn't work right
    private final Opportunity o;
    private String errorMsg1 = '';
    public newTransactionController(ApexPages.StandardController stdController) {
        this.o = (Opportunity)stdController.getRecord();
    }
 
    // Code we will invoke on page load.
    public PageReference autoRun() {
 
        String theId = ApexPages.currentPage().getParameters().get('id');
 
        if (theId == null) {
            // Display the Visualforce page's content if no Id is passed over
            return null;
        }
 
        for (Opportunity o:[select id, name, ChargentSFA__Charge_Amount__c, Check_Date__c, Check_Number__c, Check_Received_On__c from Opportunity where id =:theId]) {
            if(o.Check_Date__c == null || o.Check_Number__c == null || o.Check_Received_On__c == null || o.ChargentSFA__Charge_Amount__c == 0){
                return null;
            }            
            ChargentSFA__Transaction__c checkPayment = new ChargentSFA__Transaction__c();
            checkPayment.ChargentSFA__Opportunity__c = o.id;
            checkPayment.ChargentSFA__Amount__c = o.ChargentSFA__Charge_Amount__c;
            checkPayment.Check_Date__c = o.Check_Date__c;
            checkPayment.Check_Number__c = o.Check_Number__c;
            checkPayment.ChargentSFA__Payment_Method__c = 'Check';
            checkPayment.RecordTypeId = '012A0000000plkxIAA';
            checkPayment.ChargentSFA__Response_Status__c = 'Approved';
            checkPayment.ChargentSFA__Type__c = 'Charge';
            insert checkPayment;
        }
 
        // Redirect the user back to the original page
        PageReference pageRef = new PageReference('/' + theId);
        pageRef.setRedirect(true);
        return pageRef;
 
    }
    
}