I have a Powerbook G4 1.67GHz and have a similar problem, but I'm not sure it's exactly same. The computer randomly freezes, though in my case the mouse freezes too. That's what makes me think my issue could be different. I had my Powerbook for seven months before the problem started. I've wiped out and reinstalled and tried a bunch of other test with no luck. It can occur twice a day or not for a week at a time. I've even started a log of running apps, actions, everything to see if I can find the common denominator. No luck yet though.

I ran across this in some previous searching. This is an older post, but people in the Apple discussion referencing the command key made me think of it.

Used to happen alot on my MBP, not so much lately. Not sure what changed. It's incredibly frustrating though. I shouldn't have to hard reboot my machine simply because I dared to perform such a mediocre task as CMD+Tab.

I used to run into this problem all the time (well, it felt like all the time) before switching to LiteSwitch X, a nicer window switcher that's worth it for the force-quit and force-relaunch features of the application alone.*

After having installed LiteSwitch X, it seems the freeze problem has decreased a good bit. Sometimes the window switching gets sluggish, but after relaunching LiteSwitch from the preferences panel, all is well. Try the app--I think you'll like it.

I love Apple, generally, but when something is buggy it sure is a pain. Of course, I've had my own problems with my MacBook lately....

*I'm not associated with the makers of this app, I'm just a happy user!

It's a graphics card issue. I'm almost 100% positive on this - I think they switched graphics cards in their laptops in early November (I seem to remember reading this somewhere). It's possible that a driver replacement could fix it; hard to say.

it happens occasionally on my mac g4 dual 2g, but never on my MBP.

Unfortunately I don't have any reason or fix, but wanted to add my 2 cents to show it goes back farther than the graphic card switch.

hit shift+command+tab

that fixed it for me

MacBook, and before that 15" PowerBook G4: no, never. I mean not once ever, andI I'm a rampant cmd-tabber. It's how I always switch been apps. (Exposé? What's Exposé?) Possible all of you with the problem are running some system addition or hidden login item that is causing a conflict of some sort.

12" Powerbook G4. I'm a frequent command tabber, and I've never run into this problem.

I have a 1.25GHz PowerBook and a new 2.33 Core 2 Duo MacBook Pro and haven't had any trouble with command tab. I don't use it as much these days as I used to, probably only a few times daily.

I don't have a problem with cmd-tab, but I have run into a weird situation where f3-f5 don't always control the system volume, nor does the menu bar control, nor system preferences. But I'd rather have flakey volume than a crashing system--sorry to hear about your troubles.

My guess is that it's happening when pressing Command-Esc, and not Command-Tab. You often hit Command-Esc when using the app switcher because it dismisses it, so it's easy to confuse the two. And, since NVRAM can be set up to make Command-Esc the NMI sequence, it's not too hard to get into a state where Command-Esc appears to freeze the machine.

If that is the case then the fix is easy: reset NVRAM. (Boot with Command-Option-P-R held down until you hear the chime twice.) This resets the NMI to its default which is Command-power button.

It's definitely not because of pressing Cmd-Esc.

12" Macbook here. Haven't had this problem yet, and coming from a Windows background, Cmd-Tab is practically second nature to me, something I'd easily do hundreds of times a day. Then again, after waiting for two months to get this machine fixed, guess I don't need more problems for a while.

I have a 1.5 GHz 12" powerbook, and I've never had that problem- and I'm a freak on the Command-Tab. I hope you find an answer, that's gotta be annoying...

I've had a 15" Macbook Pro for about a month and I'd say it's happened about 10 times.

Don't know if this means anything, but it tends to happen if I've been idle for a while, left the room or something.

I mention this because a similar temporary freeze-up has happened when I am trying to enter my password to get out of the screensaver (only after being away from the computer for a while -- it doesn't happen if I start the screensaver manually with a hot corner).

I have a 17" MacBook Pro and haven't had that problem... yet. I've had mine for about 6 months too. I wonder what the problem is and why it happens on some and not others...

nope. big cmd+tab user. never had a problem.

I'm the author of the post about powerbook freezes mentioned in the first comment; inspired by this discussion I will shortly post a follow-up to note that since my high-tech yogurt-lid repair I have had NO problems at all, which leads me to believe my problem was purely mechanical.

Good old (ok, slow) 550 MHz PB.

I'm having the same problem on my 15" MBP with 2GB of RAM. It seems to always happen when I am switching to or from Firefox, but maybe that is just the application that has the largest memory footprint.

If I ssh in remotely, nothing seems to be taking up CPU. Killing Firefox or any other app doesn't solve the problem. The processes never exit; they remain in the Z state with a start time of 1969.

If I kill the WindowServer process, then my hung session is logged out, and all of the applications running in that session are killed. I can log back in on the console and everything is back to normal.

All of that makes me believe it's a bug in the UI code somewhere.

I have had my MacBook Pro since May (or June) and No problems at all.

I have a MBP 2.0 with 1.5Gb in Ram, I used to use it quite often as I used to be a Windows user too (I still use Windows at work), but now I almost always use Expose.

Often, I catch myself trying to do the same trick at work... then I remember that I have to Alt-tab. =)

I have an iBook G4+. I've never had such a problem.

Like has been suggested above, could it be a hardware problem due to the graphics card?

Just a followup: it happened to me twice yesterday when I was switching between apps using the mouse. For me, at least, it's not related to Cmd-Tab. Oh, and I use an external keyboard, so for me it's not related to crushing a cable.

The first time I had a second machine handy and so I logged in remotely and killed the window server process. The second time I just power cycled.

One other possibly coincidental data point: it seems to happen most frequently when I am using TextMate. Before I started using TextMate 5 months ago, i don't think I had this problem. I have noticed that sometimes TextMate grows to over 500M, and I believe the problem occurs when the OS has to start swapping. But again, that might just be a coincidence.

Our 15" PowerBook G4 purchased in Nov 05 also freezes. It has frozen even when the command key is not being used. It freezes once every several days or so under our normal use. Our local Apple dealer was unable to determine anything wrong with our machine. Compared to PCs and other laptops we own, this Mac is lousy in terms of stability. Pretty incredible given that it's 2006. I'm about at the point of getting rid of this machine and going with a product from a different vendor.

Well, see this resource...