[Splines]

I've seen a test version of an app cause issues such that the launcher would crash (i.e. "respring"). Probably some intersection of particular api usage and OS bugs.

To the unobservant user it looks like the OS is rebooting, although it's much quicker than a real reboot.

[brazzledazzle]

I've seen the same thing with an ActiveSync bug. Much quicker but you lose the running context of any apps just the same.