[Eric Westfall]

Thank you for the reply. I gave all computer specs when registering, so sorry for not including that. It's a 12.5" mid-2010 iMac. 500 G hard drive, 12 Gig of Ram, running El Capitan. I was told 30.06 GHz, I assumed that was the clock rate. (Maybe I misheard.)

This has never happened before with 48k sessions, only these which are 96k. It doesn't happen at a specific place in a song, and it'll happen with any song. Usually plays fine for 10 or 20 minutes, sometimes less, and then starts crackling very loudly, followed by the beeps. The sessions play fine on the client's computer.

What is meant by trashing prefs?

I will try the things you suggested. Thanks for your help.