Sound keeps repeating (stuttering)

Yesterday while I was watching a YouTube video the sound started glitching. There are two kinds of glitches:

1. The most common kind is where the sound repeats an approximately 1/4 second bit of sound for around two seconds, then plays normally (beginning from where it would have been had it not been repeating) for another two seconds. Then it repeats ad nauseum.
2. Occasionally, it the sound will repeatedly pause for a fraction of a second. This isn't so annoying as I don't miss any content. This second option seems to only occur when playback is started while CPU usage is low. However, low CPU doesn't guarantee this option.

I originally blamed Adobe Flash. However, killing it didn't fix anything. Then I noticed that PulseAudio was consuming a lot of audio during the glitches. So, I killed it. No dice. I rebooted. No dice. I decided to test another program, so I tried Rhythmbox. The same problem occurred, but with less frequency.

What's going on here?

Partial output from lshw:

*-multimedia
    description: Audio device
    product: 82801H (ICH8 Family) HD Audio Controller
    vendor: Intel Corporation
    physical id: 1b
    bus info: pci@0000:00:1b.0
    version: 03
    width: 64 bits
    clock: 33MHz
    capabilities: pm msi pciexpress bus_master cap_list
    configuration: driver=snd_hda_intel latency=0
    resources: irq:48 memory:fe020000-fe023fff