Problematic USB hubs can wreak havoc under Mac OS X 10.4.x

On numerous occasions we've covered issues stemming from the presence of defective USB hubs. In most cases, the issues are device specific -- iPods failing to attain a proper charge or synchronize properly with USB 2.0 hubs, for instance.

We've recently seen an increasing number of reports indicating that malfunctioning USB hubs can also cause other, seemingly unrelated issues, including problems launching applications or performing other routine tasks.

What appears to be happening in these cases are stalls or other errors in the queries that Mac OS X applications, or Mac OS X components send through the USB framework. When the problematic hub is encountered, stalls or complete freezes can occur.

In some cases, different releases of Mac OS X can harbor varied sensitivity to defective USB hubs, so that a user running Mac OS X 10.3.x with a seemingly functional USB hub will suddenly experience significant issues after upgrading to Mac OS X 10.4.x.

Take the case of MacFixIt reader Gerry Brown:

"My home network consists of two serious development machines. One is a Cube running the 7457 1.3 GHz G4 with 2 MB L3 cache, 1.5GB memory and a 120GB HD. The other is a Shuttle PC running a 2GHz Athelon with 1.5GB memory and 200GB hard drive. The systems are tied together with a Compucable A-B switch the controls a Mac keyboard, Microsoft Wheel Mouse and a 19 inch NEC flat panel. Life was good.

"That was until I installed Tiger. From that point on my Cube started acting very weird. After waking from sleep, the apps would not work correctly. It appeared as if the permissions were wrong on my home directory. When any app started, it appeared to be running from scratch without all my settings. I couldn't save data. Mail could not store any messages, etc. You can imagine my angst.

"I tried scorched earth. A clean install of Tiger from an erased hard drive. I tried a new machine. I bought a Mac Mini (returned it in 2 days when the same problem existed). I posted on boards. I created a new user account. Nothing worked.

"I bought a D-Link USB/Bluetooth device so I could sync my new cell phone. This seemed to make the problem worse. Now when the system woke up (triggered by a mouse press), the mouse would not work.

"I had focused on either Tiger or my highly modified Cube. No deductive reasoning worked.

"What I didn't think of was that the problem could be with one of the three powered USB hubs that I use. One was specifically for the single USB connection on the A-B switch. I bought a cheap off-brand powered USB hub for the devices. That was the problem. I replaced that with a new powered hub and everything is working.

"So when the experts say to get rid of all your peripherals except the essentials, when debugging problems; listen."

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