5 Replies Latest reply: Apr 15, 2012 10:05 AM by BDAqua
botonzico Level 1 (0 points)

I've gone for hours through all kinds of forums without finding a proper answer, so here I am.

This morning I've installed OS Snow Leopard 10.6.3 on my iMac, previously I had OS Tiger 10.4.11 running. Everything seemed fine until I restarted and then I started getting "USB drawing too much power" promps all over the place even though the only thing that's attached to the iMac is the keyboard and the mouse (they both work fine). The process went like this:

  • The iMac is a 2.4 GHz Intel Core Duo from october 2007
  • First I did an upgrade of my RAM, from 1GB to 2GB, that went ok.
  • Then I runned the install dvd for Snow Leopard, I did not perform a clean install, just did it over my old data. After restart, everything worked but i got this USB warning message, one of them. At that point my usb's still worked, (even though the warning) I could print and scan. To get rid of the warning, i resetted the PRAM and SMC, as suggested everywhere. After doing so, the promps multiplied and my usb ports ceased working, except for the keyboard and the mouse attached to it.
  • I've done the Apple Hardware Test, and it gives no malfunctions.
  • Firewire works fine, Isight buildt-in camera and bluetooth too.
  • I've tried all usb's and the keyboard will work in all of them, not like my printer and scanner which are completely ignored.
  • USB power warning also appears at restart with no deviced connected (no keyboard and mouse, i've tried).
  • I've also found in many forum entries  the possibility of a problem on the logic board, but since i've never had a problem with my imac until today i would not be sure about a hardware malfunction.
  • The last thing i've found around that could be a clue is something about the kernel extensions, but that's complete chinese for me, I'm  a mac plug&play user and not too much of a mac expert.

Does anybody have an idea about what could be going on? Should I perform a clean install of snow leopard? Would that solve the problem?

Many thanks in advance to the community for the help, I'm quite lost since I've owned macs for the last 15 years and this is the first problem I have with one.

iMac, Mac OS X (10.4.11)
  • BDAqua Level 10 (122,296 points)

    Do you get the USB warning if you boot from the Install Disc?

  • botonzico Level 1 (0 points)

    Thanks for the interest BD. This morning I started my imac and again got five or six USB warnings in a row. But this time my periferials worked, and my bluetooth didn't, it was completely deactivated. I did a boot from the installation disk following your question, and from the installer's Disk Utility I performed a "Verify disk" check and got no errors. Also no USB warnings in there. Then I quit the installer an rebooted from my HD volume, and the first thing I got on the screen after the grey apple was the USB warning. But at this point was again only one, and my periferials are working and my bluetooth too.

    Has all this erratic stuff any meaning to you? Is it safe that I just keep going on ignoring the warnings, or they have a reason? Or is the only reason that my imac went bananas after the upgrade?

  • Texas Mac Man Level 8 (46,565 points)

    USB and FireWire Quick Assist



    Common fixes for USB device issues (unrecognized, etc.)



     Cheers, Tom

  • botonzico Level 1 (0 points)

    Thanks Tom , I've already read the first article and tried everything on it, but the second one has a couple of things i didn't tried yet (I already went through the most obvious ones like clearing caches, checking connections, doing PRAMs, plug/unplug, etc) The USB prober test and the revert of kernel extensions sounds very misterious, but I'll give it a try. Also the firmware update looks like a good idea!

  • BDAqua Level 10 (122,296 points)

    I think it's serious, but if it didn't do it booted from Install Disc then Software is highly suspect.


    One way to test is to Safe Boot from the HD, (holding Shift key down at bootup), run Disk Utility in Applications>Utilities, then highlight your drive, click on Repair Permissions, Test for problem in Safe Mode...


    PS. Safe boot may stay on the gray radian for a long time, let it go, it's trying to repair the Hard Drive


    Reboot, test again.


    Did we get the warning in Safe Mode?