Continuous ALSA underruns

Whenever I play a score, the produced sound is complete gibberish and end quickly. For one sheet of piano music, the playback lasts about 3 seconds. If I turn down the tempo to 10%, it sounds as if the song is playing back extremely fast. Additionally, while sliding the volume control, the playback bar jumps quickly around the piece, but otherwise progresses at a normal pace.

I can export sound files and MIDI files that play perfectly in other programs, so I think this is an issue with the built-in synthesizer and pulseaudio.

Upon running the program from the console, I get this:

PulseAudio found, but no need to suspend. Starting mscore.real...
ALSA lib pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.rear
ALSA lib pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.center_lfe
ALSA lib pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.side
bt_audio_service_open: connect() failed: Connection refused (111)
bt_audio_service_open: connect() failed: Connection refused (111)
bt_audio_service_open: connect() failed: Connection refused (111)
bt_audio_service_open: connect() failed: Connection refused (111)
ALSA lib pcm_dmix.c:961:(snd_pcm_dmix_open) The dmix plugin supports only playback stream
ALSA lib pcm_dmix.c:1022:(snd_pcm_dmix_open) unable to open slave
ALSA lib pcm_dmix.c:961:(snd_pcm_dmix_open) The dmix plugin supports only playback stream
Cannot connect to server socket err = No such file or directory
Cannot connect to server request channel
jack server is not running or cannot be started

Followed by a continuous spam of these messages:

ALSA lib pcm.c:7843:(snd_pcm_recover) underrun occurred

I'm using version 1.2, on Xubuntu 13.10, 64 bit. I used to have no issues prior to 13.10, but just recently this started happening. Sometimes I get lucky and have no issues, but for the majority of the time there is seemingly no way to fix this. Any ideas?