[SalesForce] Why does the returned PageReference not work

I created two apex pages to test clicking a button to change pages and it works fine. but my cancel button just refreshes the page. can anyone please explain why this isn't working or what I need to do to get it to work

public class custNewCase {
Public String acctName {get;set;}
Public List<SelectOption> symptoms {get;set;}
Public List<SelectOption> asset250 {get;set;}  
Public List<sm1e__smEquipment__c> smEq {get;set;}
Public String ncSubject {get;set;}
Public String ncDescription {get;set;}
Public String usrid {get;set;}
Public User usr {get;set;}
Public String errMsg {get;set;}
Public String retURL {get;set;}
Public List<Account> acct {get;set;}

public PageReference cancelNC() {
  PageReference pr = new PageReference('/apex/CustomerCaseTView');
  pr.setRedirect(true);
  errMsg = 'Clicked cancel button';
  return pr;
}

public PageReference gotoP2() {
  PageReference pr = new PageReference('/apex/RP2');
  pr.setRedirect(true);
  return pr;
}

public PageReference retP1() {
  PageReference pr = new PageReference('/apex/RP1');
  pr.setRedirect(true);
  return pr;
}

public void fillDD() {
  usrid = UserInfo.getUserId();
  usr = [Select AccountId From User Where id=:usrid];
  acct = [SELECT Name from Account WHERE id=:usr.AccountId];
  If (acct.Size() > 0) { acctName = acct[0].Name; }
  else { acctName = 'No Account Assigned'; }
  symptoms = new List<SelectOption>();
  symptoms.add(new SelectOption('None','-- Select from list --'));
  Schema.DescribeFieldResult fr = Case.Symptom__c.getDescribe();
  List<Schema.PicklistEntry> pl = fr.getPicklistValues();
  for(Schema.PicklistEntry p : pl) { symptoms.add(new   SelectOption(p.getValue(), p.getValue())); }
  asset250 = new List<SelectOption>();
  try { smEq = [SELECT ID, Name FROM sm1e__smEquipment__c WHERE sm1e__Account__c=:usr.AccountId And sm1e__AssetRecordType__c='S250' ORDER BY Name];
If (smEq.Size() > 0) {
  for(sm1e__smEquipment__c sm : smEq) { asset250.add(new SelectOption(sm.id, sm.name)); }
}  
} catch (Exception e) { errMsg = e.getmessage(); system.debug(e); }
}

}

the gotoP2 and retP1 functions work absolutely perfectly in simple vf pages with a button to switch back and forth but the cancel button on this page just refreshes the page and doesn't change the url to the CustomerCaseTView page

`<apex:page standardStylesheets="false" sidebar="false"     controller="custNewCase" action="{!fillDD}">
<apex:stylesheet value="{!$Resource.CustViewCSS}"/>
<apex:form id="frm" style="line-height:1.4;">
<br />
  <apex:pageBlock >
  <apex:pageBlockButtons location="top">
    <apex:commandButton action="{!cancelNC}" value="Cancel"/>

  </apex:pageBlockButtons>
<table width="100%"><tr><td width="30%">
<font size="4">Creating new Service Case for:<br />{!acctName}</font></td>
<td>

</td></tr></table><br />
<table width="100%">
  <tr><td style="width:10%;text-align:right;"><b>Asset:</b></td>
    <td><apex:selectList style="padding: 2px; margin: 5px;" id="asset250" value="{!asset250}" size="1">
      <apex:selectOptions value="{!asset250}"/>
    </apex:selectList>
</td></tr>
<tr><td style="width:10%;text-align:right;"><b>Subject:</b></td><td>    <apex:inputText style="width:500px" value="{!ncSubject}" id="subject"/></td></tr>
<tr><td style="width:10%;text-align:right;"><b>Symptom:</b></td>
<td><apex:selectList style="padding: 2px; margin: 5px;" id="symptom" value="{!symptoms}" size="1">
      <apex:selectOptions value="{!symptoms}"/>
    </apex:selectList>
</td></tr>
 <tr><td style="width:10%;text-align:right;vertical-align:top;"> <b>Description:</b></td><td><apex:inputTextarea style="width:500px;height:100px;" value="{!ncDescription}" id="desc"/></td></tr>
</table>
Error Message: {!errMsg}
</apex:pageBlock>
</apex:form>
</apex:page>