Comment 8 for bug 474543

This patch here might fix the issue, but I would like to get a idea about the root cause of it first (hence the apt-cache policy output).

=== modified file 'DistUpgrade/DistUpgradeCache.py'
--- DistUpgrade/DistUpgradeCache.py 2009-10-09 13:26:52 +0000
+++ DistUpgrade/DistUpgradeCache.py 2009-11-06 08:58:57 +0000
@@ -557,7 +557,10 @@
                 not (pkg.isInstalled or pkg.markedInstall) and
                 not pkg.name in removeEssentialOk and
                 pkg.priority in need):
- self.markInstall(pkg.name, "priority in required set '%s' but not scheduled for install" % need)
+ try:
+ self.markInstall(pkg.name, "priority in required set '%s' but not scheduled for install" % need)
+ except:
+ logging.exception("markIntall failed")

     # FIXME: make this a decorator (just like the withResolverLog())
     def updateGUI(self, view, lock):