Is it possible?

I'm trying to install 2 (two) NetBSD in the same disk, so I want choose
one of then with bootmanager. This is because I want to play with
-current, but I don't want to lose all data if I make a mistake.

So, I have on NetBSD partition and his labels, and I made another NetBSD
partition with your labels too and installed the second NetBSD on it. The
bootmanager was installed with no problem too.

But at the boot time, I have:

F1: NetBSD
F2: -current

The F2 doesn't boot. It's something like, if I type F2, bootmanager stops,
and F1 doesn't boot too. To boot F1, I must reset the machine and  type F1
first (as I said, if I type F2 first, bootmanager stops).

What's wrong?

Thank you.