JLC: I use a USB hard drive. On initial setup/back up it took an hour or so, IIRC. After that, only a couple minutes.

Yes, that what I normally experience. But TM has been running for three hours so far, and has written a total of 2.73 GB. I can't believe that is normal. Hardware errors? Driver problems?

Hmmmm. I just thought to check the Console log file. It shows several dozen messages that look like this:

10/4/12 10:50:50.000 AM kernel: IOSurface: buffer allocation size is zero

Checking the internet, I see that no one (yet) has any firm grasp on what this means, probably including Apple. It may be related to the most recent update of Mountain Lion. Some people are having system crashes, but that hasn't happened to me (yet). This does not look good.

Loren