Overdub not recording

When over dub is turned off everything records fine with the second rack but I need to be able to hear it for it to work. When overdub is turned on it record for like one millisecond then shuts off. Anyone know what the problem is here?

For some reason your system is unable to record and play at the same time.

From the information provided that’s all I can say.

I have the defulat playback on my ssytem and a USB Yeti BLue microphone for recording. I am running Ubuntu 12.04. What other information would help you?

Do you have the default, unmodified Ubuntu sound system (PulseAudio)?

Are you able to play back from Audacity when not recording?

What settings do you have in the Device Toolbar? http://manual.audacityteam.org/man/Device_Toolbar