When I'm trying to use extensions to a custom controller in VF page, i'm getting the follwing error.What is meant by it?

"common.apex.runtime.bytecode.BytecodeApexObjectType cannot be cast to common.apex.runtime.impl.ApexType"

Receiving this error when editing a visualforce page in sandbox through developer console or third party IDE.  This page has been working in production for some time. Both page and controller are set to version 32 in sandbox and production. 
The page can be edited directly through Develop->Pages.

Here's a very simplified version of the page which produces the error
 

<apex:page standardController="User" extensions="SalesRepGoalController2"> 

<b>Hello World!</b>
</apex:page>

and controller
 

public with sharing class SalesRepGoalController2{
private String userID = '' ; 	
public SalesRepGoalController2(ApexPages.StandardController c)
	{
		userID = c.getId(); 
	}
}

Java 1.7 was installed, but has been uninstalled.

Windows 8 Enterprise,  64bit
IE 10
JRE none