I assume that's 5v 1000mA (or 1A). That should be enough.
Do you have caps-lock pressed? It should be off. You probably don't, but its always worth checking.
How are you shutting down the pi? Pulling the plug while its writing to the SD card can sometimes cause corruption.
Are you putting in the right password? raspberry, not strawberry.
Multiple incorrect logins should not cause a kernel panic. Have you tried a different SD card?
I'm running out of the obvious things to try.

Karl.