Well, I had a similar problem about a month ago. I went to wash my car, got in to start it and got the same loud clicking and no cranking. I disconnected the neg. terminal for 5 minutes, reconnected and it started up fine. I haven't had any issues since.
HOWEVER, when that happened, it caused a short somewhere because my door locks started engaging every 2 seconds or so. So, I pulled the power door lock fuse so that I didn't at least have the damn door locks constantly engaging.
Today I had to change a flat tire and it started up fine before changing the tire. I jacked it up, changed the tire, put it back down.....and nothing, just that clicking sound when turning the key. The headlights are just slightly dimmer when I turn them on. The interior lights are significantly dimmer when turned on.
Im going to put another battery in tomorrow and see what happens.