Error: Could not find which method getAt() to invoke

Hi there,
I'm suddenly getting the following error when I execute

Tue Jan 25 14:22:00 NZDT 2011:ERROR:org.codehaus.groovy.runtime.metaclass.MethodSelectionException: Could not find which method getAt() to invoke from this list:
public java.lang.Object java.lang.Object#getAt(java.lang.String)
public java.lang.Object groovy.util.slurpersupport.GPathResult#getAt(groovy.lang.IntRange)
public java.lang.Object groovy.util.slurpersupport.GPathResult#getAt(int)
org.codehaus.groovy.runtime.metaclass.MethodSelectionException: Could not find which method getAt() to invoke from this list:
public java.lang.Object java.lang.Object#getAt(java.lang.String)
public java.lang.Object groovy.util.slurpersupport.GPathResult#getAt(groovy.lang.IntRange)
public java.lang.Object groovy.util.slurpersupport.GPathResult#getAt(int)
at groovy.lang.MetaClassImpl.chooseMethodInternal(MetaClassImpl.java:2865)
at groovy.lang.MetaClassImpl.chooseMethod(MetaClassImpl.java:2800)
at groovy.lang.MetaClassImpl.getNormalMethodWithCaching(MetaClassImpl.java:1229)
at groovy.lang.MetaClassImpl.getMethodWithCaching(MetaClassImpl.java:1135)
at groovy.lang.MetaClassImpl.tryListParamMetaMethod(MetaClassImpl.java:1068)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:908)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:886)
at groovy.lang.DelegatingMetaClass.invokeMethod(DelegatingMetaClass.java:149)
at org.codehaus.groovy.runtime.callsite.PogoMetaClassSite.call(PogoMetaClassSite.java:39)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:40)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:116)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:124)
at Script1.run(Script1.groovy:15)
at com.eviware.soapui.support.scripting.groovy.SoapUIGroovyScriptEngine.run(SoapUIGroovyScriptEngine.java:96)
at com.eviware.soapui.support.scripting.groovy.SoapUIProGroovyScriptEngineFactory$SoapUIProGroovyScriptEngine.run(SourceFile:88)
at com.eviware.soapui.impl.wsdl.teststeps.WsdlGroovyScriptTestStep.run(WsdlGroovyScriptTestStep.java:148)
at com.eviware.soapui.impl.wsdl.panels.teststeps.GroovyScriptStepDesktopPanel$RunAction$1.run(GroovyScriptStepDesktopPanel.java:274)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)

When I execute the following code:

[code=php:nhdcamcv]import java.util.regex.Matcher
import java.util.regex.Pattern

def xmlSlurper = new groovy.util.XmlSlurper()  
def response1 = xmlSlurper.parseText(context.expand('${GET Items#Response}'));
log.info "Response: "+response1 
Pattern myRegex = ~/^s*(+|-)?((d+(.dd)?)|(.dd))s*$/


def arrayOfItems = response1.Items.Item 
log.info "Array of Items: " +arrayOfItems
for (n in arrayOfItems)
{

    log.info arrayOfItems[]
 if (n.PurchaseDetails != ''){
         log.info " PurchaseDetails: "+n.PurchaseDetails.UnitPrice
         Matcher purchaseDetailsMatcher = myRegex.matcher(n.PurchaseDetails.UnitPrice.toString());
         assert purchaseDetailsMatcher.matches()    
     }
 
 if (n.SalesDetails != ''){
         log.info " SalesDetails: "+n.SalesDetails.UnitPrice
         Matcher salesDetailsMatcher = myRegex.matcher(n.SalesDetails.UnitPrice.toString());
         assert salesDetailsMatcher.matches()    
     }
 
}



 [/code:nhdcamcv]