Occasionally, on rebooting my phone, I notice that half-a-dozen or so apps have gotten "corrupted". Their icons on my desktop become 'generic" (a green droid) and the app won't start. I can see 'remnants' of the apps when I go into Settings/Applications/Manage Applications--where they have generic "SD" icons. I generally have to re-install these apps to get them to work again. Any idea what's happening here?