Problem with USB 2.0
On various (early?) T40 models, USB 2.0 may not function, or may function only at USB 1.1 speeds. Symptoms include inability to connect to USB 2.0 devices at USB 2.0 speeds, the "This device can perform faster" pop-up in Windows XP, device ID assignment error messages from the Linux kernel, and frequent reboots of the USB bus and connected devices.
So far, two possible causes have been suggested. In both cases, replacing the system board is the only solution.
Fried Southbridge USB controller
The Southbridge chip (containing the USB controller) may have been damaged by static electricity:
Mechanical Damage to Mainboard
Mechanical damage (from bending, dropping or vibrating the laptop) can lead to components becoming desoldered from the mainboard and no longer having reliable electrical contact:
The same behavior has also been observed on a T42, where the EHCI controller stopped working after structural damage to the laptop. Plugging in a USB 2.0 capable device will yield the following error in dmesg:
Flexing the right palmrest area up will temporarily make the USB 2.0 recognizable again. Tightening the screws on the bottom and front edge of the laptop may also fix the problem.
Clearly, this is an electrical problem and not static electricity.
This seems to be a hardware problem with the USB controller on Intel's chip or related electronics. Sending the laptop in for service may help.
If the Linux kernel refuses to register the USB device, you can try removing or disabling the ehci_hcd part. Doing this means that USB devices will run at USB 1.1 speeds, which is supported by pretty much every USB device for backwards compatibility. This is not a problem for USB Keyboards and Mice as they are typically USB 1.1 anyway, but for USB storage devices it can slow things down dramatically.
If the ehci_hcd support in your distribution is built as a loadable module, you can simply unload it with
# modprobe -r ehci_hcd.
To unload it automatically on bootup, you can add the above command to /etc/rc.local.
Or alternatively to prevent the module from ever loading, add ehci_hcd to /etc/modprobe.d/blacklist.conf (or /etc/modprobe.d/blacklist). But note that adding it to the blacklist file might not be enough by itself as most distributions load the ehci_hcd module already during initrd, as such you might need to rebuild your initrd after adding it to the blacklist for it to have effect.
To rebuilt your initrd on a Red Hat/Fedora system, run the following command
mkinitrd -f /boot/initrd-$(uname -r).img $(uname -r)
If your distribution (like Fedora 11) instead compiled the ehci_hcd support directly into the kernel, you cannot unload or blacklist it.
In such cases you can unbind it in sysfs, but first we need to find what the PCI device number of the EHCI controller is as follows;
lspci|grep -i ehci
On a ThinkPad T41 this returns
00:1d.7 USB Controller: Intel Corporation 82801DB/DBM (ICH4/ICH4-M) USB2 EHCI Controller (rev 01)
To unbind the ehci_hcd support from the PCI device, run the following command (adjust PCI location, based on lspci result)
echo -n "0000:00:1d.7" > /sys/bus/pci/drivers/ehci_hcd/unbind
To automatically unload it on bootup, simply add the last command to /etc/rc.local.