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lhmd Level 1 Level 1
Someone must know how to kill the offending process (I hope).

This problem has been around for a few years now (i.e., both in Panther and Tiger) - but unfortunately, no one that I know of has posted a solution on the net as to how to recover usual operations from those times when the 'Application Switcher' (i.e., the one activated by command-tab) is stuck on screen.

The only thing that moves on screen is the mouse (usually stuck as a hand for me). No other keyboard shortcut makes any difference. I can ssh into the machine from another computer. But killing the dock, Finder or similar apps leaves zombie processes around and does not bring the gui back to life.

It seems to occur if you are too quick for the system (i.e., are able to command tab fast enough either to have done so before the panel appears on screen or have let go of the command key prior to it being able to get its required resources or something).

The only process on the system that has this problem of locking up the machine is the application switcher - there must be some way of killing when it hangs when such a thing occurs, but I've no idea what to kill.

Has anyone had success with recovering from this without rebooting the system from a remote system or holding down the power key?

Powerbook G4, 1.66 Ghz   Mac OS X (10.4.9)   1 Gig Ram
  • TailOfTheSun Level 1 Level 1
    I'm having the same problem. It used to occur every few days, but I hadn't seen the issue in over a week. I thought it was over until it happened again last night. I've traced back posts that were created over two years with the same problem, and it still hasn't even been acknowledged by Apple.

    http://www.joemaller.com/2006/09/19/os-x-gui-lockup-with-command-tab/
    http://simplygenius.com/geekblog/2006/01/26/os-x-ui-freeze/
    http://forums.macrumors.com/showthread.php?t=209009
    http://discussions.apple.com/thread.jspa?messageID=701265
    http://guruza.com/question/122/reward-100.00

    The only solution I've heard is to completely use a different application switcher (which is ridiculous).

    I do agree that it seems to be when I'm working too quick for the system. Because it's usually when I'm frantically trying to get something done, and the fact that my machine gets the "Command-Tab of Death" doesn't help. I'd personally rather experience a BSOD -- at least it's more meaningful.

    Macbook   Mac OS X (10.4.9)   C2D 2.0GHz
  • alphafoo Level 1 Level 1
    I have been having the same problem and it's happening more and more often-- several times a day, and always when I am most busy, switching a lot. I just installed LiteSwitch for the 30-day trial. I'll know long before then if it makes a difference.

    Would be nice if Apple would at least acknowledge this.
  • shgaki Level 1 Level 1
    I have been having the same problem for a couple of years. I have installed LiteSwitch X trial version to see whether it fixes the problem. And actually 10 minutes ago I had the problem again. Alternative application switchers do not seem to solve this problem. I would say that LiteSwitch X is an excellent application, and it's worth buying it if you want its features which are not offered by the default switcher, but anyway it's not the solution of this issue.

    Can anyone guess what the problem is when it is not in the switcher application?
  • shgaki Level 1 Level 1
    This is a follow-up of my previous post.

    I keep using LiteSwitch X trial and actually I haven't experienced any more freeze since that I reported in the previous post. Because this issue occurs sporadically, I need more days before I form the conclusion, but it is possible that the alternative switcher at least reduces the possibility of freeze. There's also another possibility that the last freeze I experienced was caused by a totally different reasons and have no connection with the issue discussed here although it looked like exactly the same problem.

    Anyway I rushed to a conclusion in the previous post. I would say it might be worth trying the alternative switcher if you are in trouble with this problem.
  • Marsipan Level 1 Level 1
    This just happened to me (again). Seems to creep up every few weeks. It's totally unpredictable.

    My MPB is connected to a Cinema Display & closed (built-in screen off). This time I was able to make the Mac sleep by opening & closing the clamshell, but upon wake, the display was just black with only the pointer (hand) still moveable with the trackpad. A hard reset got it going again.

    There was no crash log written... so I have no way to know what is causing this.

    So frustrating to get derailed by a dirty restart.
  • jdhuntington Level 1 Level 1
    I'd like to add that I also experience this problem on a semi-regular basis.

    I often use my MBP with an external cinema display.

    I've checked everything that I've heard might be causing this, but I've had no luck in solving it.

    (Possible causes such as bad ram, universal access hotkeys, specific applications open, etc)
  • wr0ng Level 1 Level 1
    Chiming in - still happening for me too ( http://simplygenius.com/geekblog/2006/01/26/os-x-ui-freeze/ )- this is really annoying, I'm getting tired of having to reset my machine so often! I've just switched to Witch for an app switcher, lets see if this helps any, but I'd much rather a fix from apple as I prefer the way the built in App Switcher works.

    Since I can ssh into my machine when the problem is exhibiting itself, I'd be happy to run any tests/diagnostics/postmortems that would help an engineer figure this out. I'm a software engineer myself, so don't be shy with any esoteric commands that would give us the slightest chance of debugging this - e.g. maybe attach to a process with gdb to get a stack trace/core dump - just need to know which ones to attach to.
  • Marsipan Level 1 Level 1
    In addition to my own experience, I just witnessed a very public App Switcher freeze at our Austin on Rails meeting. The Windows guys were laughing

    http://marsorange.blogspot.com/2007/09/very-public-app-switcher-freeze.html

    ...and my own recent experience...
    http://marsorange.blogspot.com/2007/09/another-app-switcher-freeze.html
  • Marsipan Level 1 Level 1
    Upon reading the thread again...

    Does the use of an external display make the App Switcher unstable?
  • GabrielZ Level 1 Level 1
    Me too. I've had the same problem both on my old Powerbook Pro as well as on my new Macbook Pro.
    Learning that this problem has been existing for so long is rather saddening, since i thought Apple does not make business by the M$ way, which simply doesn't care about the "last 10%" of bugs.
    That kind of nullifies that long-standing slogan "It just works".

    Best regards,
    Gabriel.
  • GabrielZ Level 1 Level 1
    That's a good question. I'll tryo to watch that.
    I can't remember observing the bug on the laptop's display (but that doesn't mean too much ).

    Best regards,
    Gabriel.
  • GabrielZ Level 1 Level 1
    Hm, according to this snapshot it does happen on the laptop's display too:
    http://marsorange.blogspot.com/2007/09/another-app-switcher-freeze.html
    G.
  • GabrielZ Level 1 Level 1
    I'm new to this thread,
    but can you kill the app switcher process when logged in remotely?

    I would be sort of half-happy if there was a way to de-freeze the machine so that i don't loose all unsaved work and open web pages etc.

    Best regards,
    Gabriel.
  • GabrielZ Level 1 Level 1
    it seems to be when I'm working too quick for the system


    I've got the same impression here.

    G.
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