diff -Naur Volatility-1.1.1/forensics/addrspace.py Volatility-1.1.1.a/forensics/addrspace.py
--- Volatility-1.1.1/forensics/addrspace.py	2007-07-29 12:38:00.000000000 -0400
+++ Volatility-1.1.1.a/forensics/addrspace.py	2008-02-27 12:46:10.000000000 -0500
@@ -61,6 +61,8 @@
         return [self.get_address_range()]
 
     def is_valid_address(self, addr):
+        if addr == None:
+	    return False
         return addr < self.fsize - 1
 
     def close():
diff -Naur Volatility-1.1.1/forensics/x86.py Volatility-1.1.1.a/forensics/x86.py
--- Volatility-1.1.1/forensics/x86.py	2007-07-30 17:29:06.000000000 -0400
+++ Volatility-1.1.1.a/forensics/x86.py	2008-02-27 12:47:01.000000000 -0500
@@ -147,6 +147,8 @@
         return longval
 
     def is_valid_address(self, addr):
+        if addr == None:
+	    return False
         phyaddr = self.vtop(addr)
         if phyaddr == None:
             return False
@@ -270,6 +272,8 @@
 	return longlongval
 
     def is_valid_address(self, addr):
+        if addr == None:
+	    return False
         phyaddr = self.vtop(addr)
         if phyaddr == None:
             return False