I have been playing with it and still no luck. Now I have a even more weird problem. To summarize what I did in the following:
1. Started off with the log in problem as stated in the question, I then went ahead to download the official Ubuntu build for PC2 and I don't even see the out put to monitor. The monitor has no output. Originally I thought it would be my monitor problem as this is a different one I used.
2. Then I took the PC2 (and a Prime) to the monitor that used to work (just can not log in) and weird enough that there is no output. So I thought maybe the official build does not work, then I switched to use the SD card from my own build (use to book fine just not able to log in) and it didn't show anything either.
3. Then I used the SD card used to boot fine for both PC2 and Prime, both failed to display anything on the monitor.
So now I got stuck at using both official images and my own built images for both PC2 and Prime, non works.
I am intrigued There must be something very basic I have missed.
Any suggestions what to do next?