The celebrated jumping mouse of Lion

I haven’t seen any of the major Mac blogs mention it, so I guess it isn’t a widespread problem, but I’ve had the “jumpy mouse” or “jumpy cursor” problem on both my computers since upgrading to Lion.

The problem is simple: you move the pointer on the screen toward a target, and the pointer way overshoots the target, possibly going all the way to one of the corners of the screen. It’s not because you’re snapping the mouse or whipping a finger across the trackpad; you’re using the same motions ingrained by years of habit, but the pointer isn’t behaving the way it’s supposed to.

Here’s a short screen recording I did yesterday on my iMac. I’m using an Apple (née Mighty) Mouse and moving it at about the same speed during all the attempts to resize the window. The sudden jumps in window size aren’t a video artifact from the frame rate or the compression settings, they’re an accurate representation of what goes on when I move the mouse.

As you can see, the jumpiness doesn’t occur with every mouse movement. The inconsistency is almost as frustrating as the jumpiness itself.

I first noticed this on my MacBook Air—which isn’t surprising, since that’s the computer I first upgraded to Lion—while I was using the trackpad. Until I saw some of the aforelinked discussions, I thought my trackpad had gone bad. It was very jumpy a few weeks ago but then seemed to go away, which made me think the update to 10.7.2 had fixed it. I don’t really notice it on the Air anymore.

I didn’t upgrade my iMac to Lion until late last week. At first, I didn’t notice any problems, which sort of reinforced the notion that 10.7.2 was the solution. But on Wednesday and Thursday of this week, I was having terrible trouble controlling the pointer, overshooting almost every button I wanted to click. After doing that screen recording yesterday afternoon, I rebooted, which eliminated the jumpiness for the rest of the day, but it came back this afternoon.

I’ve tried to determine if some background process is the culprit, but haven’t found anything definitive. Time Machine was doing a backup on the iMac this afternoon when the jumpiness returned. I tried to stop the backup to see if that would fix the problem, but Time Machine wouldn’t stop. That’s another bug, but I didn’t feel like running down two bugs at once. Time Machine wasn’t running when I made the screen recording, so the jumpiness can’t be traced exclusively to it.

I logged out and back in again to stop the Time Machine backup. That fixed the jumpy mouse, too, but it’s an unsatisfying solution. I don’t want to have to reboot or log out and in every day.

So the upshot is this:

I hate computers.