Problems with multiple USB devices. (Possible Low Power on USB Bus)

Question

I believe I'm having an issue with the USB bus or one of my devices that I have installed on my iMac.
I purchased this iMac along with a printer (HP C4280 All-in-One) as part of a promotion deal. I also have wireless logitech USB mouse, and iPhone and an 80gb 5th Gen iPod.
My problem has to do with syncing the iPod and iPhone. Normally I have the printer attached to the iMac along with the USB mouse. Both devices function as expected. However I have problems when I connect the iPhone or iPod.
iPod Symptoms: When I connect the iPod the iPod screen shows the flashing red circle with a line but iTunes never launches and the iPod never syncs.
iPhone Symptoms: When I connect the iPhone the iPhone screen says Sync in Progress and iTunes does show the iPhone in the list of devices but a dialog appears giving me one of two messages (that I've seen so far) - [msg 1] Your iPhone is corrupt please disconnect then reconnect to restore. [msg 2] iPhone device timed out.
I've been dealing with this problem for a couple months and found that if I disconnect the printer (HP C4280) then connected either other device then everything works just fine.
I downloaded XCode 2.5 and launched the USB Prober utility. Then plugged in each device in turn and found some interesting findings.
When connecting the iPhone (1st attempt) the USB Logger reported; (iTunes displayed msg 1 from above)
128.517 [1] USB Device iPhone is violating Section 9.3.5 of the USB Specification -- Error in GetConfigDescriptor( wLength = 4)
128.520 [1] USB Low Power Notice: The device "iPhone" cannot be used because there is not enough power to configure it
128.528 [1] USB Low Power Notice: The device "iPhone" cannot be used because there is not enough power to configure it
128.629 [1] AppleIRController[0x2dc8e00]::RearmInterruptRead immediate error 0xe000404f queueing read, clearing stall and trying again(1)
When connecting the iPod (1st attempt) the USB Logger reported; (iTunes never showed that the iPod devices was connected)
938.797 [1] USB Device IOUSBDevice is violating Section 9.3.5 of the USB Specification -- Error in GetConfigDescriptor( wLength = 4)
938.801 [1] IOUSBCompositeDriver[0x39b9f80](IOUSBDevice) SetConfiguration (1) returned 0xe00002ed
938.900 [1] AppleIRController[0x2dc8e00]::RearmInterruptRead immediate error 0xe000404f queueing read, clearing stall and trying again(1)
When connecting the iPhone (2nd attempt) the USB Logger reported; (iTunes displayed msg 2 from above)
1789.023 [1] AppleIRController[0x2dc8e00]::RearmInterruptRead immediate error 0xe000404f queueing read, clearing stall and trying again(1)
1802.166 [1] AppleUSBEHCI[0x28a7000]::Found a transaction which hasn't moved in 5 seconds on bus 253, timing out!
1809.166 [1] AppleUSBEHCI[0x28a7000]::Found a transaction which hasn't moved in 5 seconds on bus 253, timing out!
I'm suspicious of the USB Low Power Notice. If this is true then I suspect the my iMac might need some type of repair. However I am also suspicious of USB Device violating the USB Spec Error. Although this is the message that appears when I plug in the iPhone or iPod I don't think I can assume that error relates to the iPod or iPhone. The error doesn't specify which USB Device is in violation.
My current workaround is to unplug the printer every time I sync the iPhone or iPod which is cumbersome. I'm also worried that repeated connecting/disconnecting of USB plug for the printer will over time damage the USB port.
I'm not sure what options I have here. Can anyone provide some suggestions or information that might provide some insight.
Best Regards,
xgnomex

Answer 1

A-Ha! Now I'm feeling like my 1.5 hours of reading this forum are not wasted, since I've found others with similar symptoms.
I've only had my iMac for two weeks today. I've got some new accessories & have experimented with the ones I've had awhile (various USB external drives). My model has 3 USB ports, one of which is taken by the keyboard, of course.
Over the weekend, I picked up an MS Office 2008 Upgrade and also an HP Officejet Pro L7680 all-in-one. I only mention the Office upgrade because I installed it on the same day as the printer, but it's possibly unrelated.
I actually have a Belkin 4-port hub--not the same one suggested in this thread, but externally powered with it's own A/C adapter. (It's a Hi-Speed USB 2.0 r-Port Hub, model F5U234 Rev.3, and I used it with a previous iMac G3 CRT with no problem.)
So with a LaCie 100 GB USB Mobile Drive in one of the iMac's ports, and the HP L7680 in the iMac's third port, or the HP via the Belkin hub in iMacs the third hub, here are some of the symptoms I've seen:
1) while browsing in Firefox, suddenly the mouse-cursor will "freeze" (get stuck) in a pull-down selector...sometimes it unfreezes, but eventually (like on the next pull-down menu) the keyboard & mouse will shut off (and if you wait & the iMac goes to sleep, the keyboard won't let me enter my unlock password when I wake the iMac with the Apple Remote)
2) when trying to open a document from the LaCie in MS Word, Word freezes and the keyboard & mouse go dead--terminal beachball--to restart the computer, I have to hold in the power button
3) when trying to print a message in Mail, Finder freezes (though the print job does finish)
These symptoms seem strange! Hey, it's just supposed to work, right? But everything has limits, so my question becomes, "how much stuff can I hook up at once?"
I wonder if this Apple article is addressing this issue:
http://docs.info.apple.com/article.html?artnum=25243
especially when it says "Two high-bandwidth devices or two isochronous devices cannot be connected to a single Universal Serial Bus (USB)."
So only two hi-speed USB devices can be connected "to the same bus" simultaneously? I'm not entirely sure I understand what "isochronous" means, but I'm thinking I need to peel my printer off the USB somehow, maybe via Airport Express--?
Does anyone know for sure about USB limitations? Thanks.
Also, xgnomex, how/where did you find that "USB Logger"? Is that something iPhone-specific, or is it an OS X log in a Library somewhere?