Difficulty recording two channels off of mixer

[revedmusic]

I have Windows Vista and an M-Audio interface. I use a microphone and my guitar is also plugged in. After I record in Audacity .1.3 I cannot record other tracks while monitoring the first tracks at the same time. Auacity will not play back anything unless the M-Audio interface is turned off. You can see that the metering is working but there is no sound. I would like to be able to overdub to fix or correct errors in the first track by playing along on a 2nd track then substituting area for another. But you cannot record new tracks and listen to an older track at the same time. I could do it when I just had a usb microphone but no interface. What is wrong. I have gone to edit/preferences/recording and checked the overdub box but still nothing. Anyone know whats wrong?

[steve]

What do you have set in the Device Toolbar?
Which exact version of Audacity? "1.3.13 Unicode"?