I think it was EggTimer's fault. It could not cope well with the phone being switched off while it was counting down. It registered an alarm with alarmd and, after power down and up, the alarm triggered, but EggTimer was not running any more so there was no one to cancel the alarm. Or something like that anyway.

SSH to the rescue. Nothing else worked, pressing Stop in the dialogue just closed the dialogue which immediately sprang back and started playing again, giving me only a few seconds to do something. Repeating it several times rebooted the device. The only thing that worked was logging in through SSH and running
It had the unfortunate side effect of deleting all my alarms; fortunately I had only four.

However, I have also noticed that my whatsitsname that pops up when you press the blue up arrow and Sym/Ctrl and allows you to type extra keys now looks like this (see below). Never mind the accented characters, that's deliberate. I am referring to the colours. Could that be the result of uninstalling ezitext?