Q: I have rooted n1. when I go to recovery to do backup, I get the triangle with the little green android guy, but phone is stuck there. I have to remove battery to reboot phone. What have I done wrong?
A: You still have the stock (shipping) recovery. If you want a different recovery (Amon RA's), download it, the from fastboot, run fastboot flash recovery downloaded_recovery.img
I'm a noob but, I had this problem too.
One of two things solved the problem.
First, I had moved ROM manager to SD from application settings, and the problem went away when I moved it back to phone.
and/or...
Second, from ROM manager there is a use alternate recovery button (Amon RA's).
After doing both of these things the triangle went away.
---------- Post added at 09:35 PM ---------- Previous post was at 08:49 PM ----------
Clearly I'm showing my noob-ness. It turns out you can hold down volume up and the power button when you get this triangle, and eventually recovery will come up.