With firmware r73078, switching to another wireless network will not prompt for password. To switch to another wireless network, you must perform factory reset.

Here's the sequence I performed:

1. Factory reset
2. Choose SqueezeTest network (WPA)
3. Choose my SBS and play local flac track.
4. Go to Settings->Advanced->Networking->Choose Network
5. Choose a wireless network. Screen immediately goes to Connecting to .. without prompting for password.
6. Connecting fails with Can't Connect screen.
7. Choosing Try again will fail.

If you select Choose a different network option in #7, and go back to choose SqueezeTest, the attempt to connect will be successful. It appears to reuse the password for SqueezeTest on the new network, thus failing.

At this juncture, to connect to another network will require a factory reset.