Here's some information on Dalvik cache:
xda-developers - View Single Post - What is Dalvik Cache?
Because, when you install, uninstall and move apps on your phone, the Dalvik cache gets full of items you no longer need, which can gum things up and cause slow-downs, I clean up my Dalvik cache using Titanium Backup every couple of days and clean it entirely once a week or so. It rebuilds itself and you don't lose any of your data (so it won't clear any of your settings, etc.).
With the altDeskClock, I believe what probably happened is that the dev inadvertently put the wrong DeskClock.apk in the altdeskclock download on his server. They're named exactly the same thing, so it's really easy to do. I'll let him know and see if I can find the right one and will put it in an update.zip for you.
I wonder if the kernel is a problem for you, because I've made numerous phone calls of varying lengths and never had my phone crash.
UPDATE: I'm attaching an update zip with the DeskClock that has the voice command functionality. Just know that it's a trade-off: the one with voice commands does not have the ability to change the clock colors.