iPod and Macs sometimes won't play nice together

iPod, MacPro, Macbook Pro all work fine (more or less) on their own. But they are temperamental, like teenagers. Well, these three devices are all teenagers.

About 4 years ago I bought a used iPod. I've been adding music to my iPod by copying music CDs into iTunes on the MacPro, then adding them to the iPod and creating "playlists" mainly as one playlist for each album. That's worked quickly, efficiently, and predictably....until now.

A couple weeks ago, various versions of failure began to occur when I connected the iPod to MacPro for the purpose of saving playlists onto the iPod via cable connected to USB port on MacPro. This seems random, on occasion it works after some protest, though not as clean and efficient as it once was.

I just succeeded with one such transfer, but the spinning beachball and error messages (syncing) suggested the mission had failed. On at least one occasion, the spinning beachball appeared WITH the message that the iPod was synching with the Mac. After about 10 minutes (didn't note the clock) that ceased and the iTunes reverted to normal....for a few minutes. Then it went into spinning beachball phase, followed by:

"The iPod "xxxxxx's iPod cannot be synced. And unknown error occurred (13010)."

I clicked "ok" and now the iTunes page looks normal again.

This is frustrating and inefficient for adding music to the iPod that I use often. Can anyone shed light on this?

Thanks!