I'm running Update 6.
Fairly frequently the Update Monitor spontaneously shows an "X" and the Update Manager is screwed up with messages similar to topic viewtopic.php?f=198&t=121976. Synaptic is also screwed up.
The problem is always resolvable as in viewtopic.php?f=198&t=114923#p638950 but it's a real PITA.
Why does it happen? Can anything be done about it?