Comment 1 for bug 534076

This part of the mixxx.log might be relevant:

Debug: [Main]: PortAudio: Started stream successfully
Debug: [Main]: iNumDevicesOpenedForOutput: 1
Debug: [Main]: iNumDevicesOpenedForInput: 0
Debug: [Main]: Displaying mixxx
Debug: [Main]: Running Mixxx
Debug: [Main]: select()
Debug: [Main]: select()
Debug: [Main]: select()
Debug: [Main]: select()
Debug: [Main]: Setting vinyl device #2's channels to: ""
Debug: [Main]: SoundManager::setupDevices()
Debug: [Main]: Building timecode lookup tables...
Debug: [Main]: Starting vinyl control xwax thread
Debug: [Main]: Building timecode lookup tables...
Debug: [Main]: Starting vinyl control xwax thread
Debug: [Main]: SoundDevicePortAudio::open() "1, /dev/dsp1"
Debug: [Main]: m_dSampleRate 44100
Debug: [Main]: iLatencyMSec: 5
Debug: [Main]: output channels: 4 | input channels: 2
Debug: [Main]: iFramesPerBuffer 256
Debug: [Main]: iLatencyMSec: 5
Debug: [Main]: Opening stream with id 1
Debug: [Main]: Error opening stream: Invalid number of channels

That's when the Dialog Error shows up.

The Log for the hang is here:

Debug: [Main]: select()
Debug: [Main]: Setting vinyl device #2's channels to: "2"
Debug: [Main]: SoundManager::setupDevices()
Debug: [Main]: Building timecode lookup tables...
Debug: [Main]: Starting vinyl control xwax thread
Debug: [Main]: Building timecode lookup tables...
Debug: [Main]: Starting vinyl control xwax thread
Debug: [Main]: SoundDevicePortAudio::open() "1, /dev/dsp1"
Debug: [Main]: m_dSampleRate 44100
Debug: [Main]: iLatencyMSec: 5
Debug: [Main]: output channels: 4 | input channels: 4
Debug: [Main]: iFramesPerBuffer 256
Debug: [Main]: iLatencyMSec: 5
Debug: [Main]: Opening stream with id 1
Debug: [Main]: Opened PortAudio stream successfully... starting
Debug: [Main]: Dynamically loaded PortAudio library!