diff -Nur -x '*.orig' -x '*~' packagekit-0.3.14/backends/apt/aptDBUSBackend.py packagekit-0.3.14.new/backends/apt/aptDBUSBackend.py
--- packagekit-0.3.14/backends/apt/aptDBUSBackend.py	2009-04-20 15:28:31.000000000 +0200
+++ packagekit-0.3.14.new/backends/apt/aptDBUSBackend.py	2009-04-20 15:29:37.000000000 +0200
@@ -32,6 +32,7 @@
 import socket
 import stat
 import string
+import struct
 import subprocess
 import sys
 import time
@@ -188,6 +189,24 @@
     Enhanced version of the apt.cache.Cache class which supports some features
     which can only be found in the consolidate branch of python-apt
     """
+    DPKG_LOCK = "/var/lib/dpkg/lock"
+
+    def __init__(self, *args, **kwargs):
+        if self._is_dpkg_locked():
+            pklog.debug("dpkg lock set, opening cache memonly")
+            kwargs["memonly"] = True
+        apt.cache.Cache.__init__(self, *args, **kwargs)
+        
+    def _is_dpkg_locked(self):
+        if not os.path.exists(self.DPKG_LOCK):
+            return False
+        flk=struct.pack('hhllhl',fcntl.F_WRLCK,0,0,0,0,0)
+        f=open(self.DPKG_LOCK)
+        rv = fcntl.fcntl(f, fcntl.F_GETLK, flk)
+        lockv = struct.unpack('hhllhl', rv)[0]
+        f.close()
+        return (lockv == fcntl.F_WRLCK)
+
     def __iter__(self):
         """
         Let the cache behave like a sorted list of packages