CBR audio???

[unknownx]

I did exactly what the xvid tutorial tells me to do for the audio... and i always get VBR audio for my xvid.. but lately.. somethin is really strange.. I use the same method but I get CBR audio!!
can someone please tell me what is wrong?

[unknownx]

btw.. when i use '--alt-preset 160'
lame seems to ignore the command and do CBR audio instead of VBR