
It turns out that Time Machine performs some sort of logging prior to performing backup operations. I guess the process can get out of hand, which can cause some problems if you are running a laptop on battery. Fortunately, there's a simple fix:
- Disable Time Machine: Go to the Time Machine pane of System Preferences, then set the switch to Off and close System Preferences.
- Kill the syslogd process: Launch Activity Monitor (in /Applications » Utilities), find and select syslogd, and click Quit Process. You will need to authenticate.
[robg adds: I did a bit of searching, and it seems this is more than an isolated incident, though it's not widespread. I would expect that, after killing and restarting syslogd, you could then restart Time Machine. However, since I haven't seen this problem, I can't test this theory.]