Comment 105 for bug 62751

I think your problem is related to using /dev/random in your crypttab

swap /dev/sda4 /dev/random swap

/dev/random collects entropy from different parts of the system (including mouse/touchpad usage). I'm not sure, but I suspect entropy is not saved at shutdown, so entropy must be collected again at start up. /dev/random will block without enough entropy, and using the touchpad is putting some entropy into the random number system.

If you want it to not block, try using /dev/urandom instead. It is not quite as secure, but I think it is more than secure enough for the key for the swap partition.

For more on the differences between /dev/random and /dev/urandom, see

$ man urandom

(On reading that it mentions a way to save entropy on shutdown, though I think you would want to change the place to save it to not in /var/run as that is a filesystem in RAM created by ubuntu on start up).