So it's not just me that has this problem with A600s then!
I have a 600 with this very problem - power light on, Caps Lock light on and stays on. Leave the machine on for about an hour and eventually it comes up just fine. I had a solution - another motherboard.... but the new motherboard had exactly the same problem! Different PSU and everything!
I suspect it's the +5V line checking circuit that's not happy but I'm not sure of that - it waits for a steady +5V with not too much ripple, then tells the rest of the machine to boot up, but it seems reluctant to do this!
If I ever find anything else out I'll let you know... could you do the same?
