MP3Encoder problems

Hello to all.

I've been playing with mod_mp3 for a few days, and I'm finding a problem 
when setting the MP3Encoder directive.

MP3Encoder "/usr/local/bin/lame -q 2 -b 160 --silent % -"

When I choose a file to stream from the select menu, I just get the 
broken Quicktime icon that means that it can't play the file.

If I try with Winamp, I get an error too.

My OS is OpenBSD 3.4, with the embedded Apache (disabled chroot).

The mod_mp3 log just shows the usual.

Is there any other directive that I should add/remove?
The configuration for my mod_mp3 is this:

        <Location /mp3z>
                MP3Engine On
                MP3DefaultOperation select
                MP3CastName "My_Radio"
                MP3Genre "Todo"
                MP3 /var/files/mp3
                 MP3Log /var/www/logs/mp3_access.log
                MP3Encoder "/usr/local/bin/lame -q 2 -b 160 --silent % -"
                MP3Allow *.mp3
        </Location>

Thanks a lot!

Gabriel.