I have a strange problem with the AE lock at the A720.
If I activate the AE lock via the key shortcut (half shutter & +/-), the CHDK UI disappears. The ALT mode is possible. Than the UI is visible again. After leaving the ALT mode the UI disappears again.
With a script it is similar. After a half shoot procedure, setting set_aelock(1) and the first shoot the UI disappears and the script waits at the position after shoot().
Other variants of shoot() produce the same situation.With the SX220 and the same script is all fine.
msl