sound starts glitching and skipping

Hi,

Under some circumstances I'm not sure about, sound playback on my iMac starts glitching and skipping. It may happen while I'm browsing, typing text or just reading or just listening to iTunes. It affects the whole system, iTunes and Safari. E.g. if it happens in Safari while I'm watching YouTube, the video continues to play smoothly wile the sound is corrupted, like the audio buffer is overflowed.

The only reasonable way to fix it I have found so far is to reload the page (if it happens in safari), or pause iTunes for a while and then resume it again. Doing this I can hear some clicks from the internal speakers like their are switched off/on.

I don't have the issue on my macbook so apparently it's a hardware issue. I tried to reset SMC and PRAM according to the official support pages, but it didn't help.