I would like to confirm this bug.

I am experiencing similar problems on Ubuntu karmic with the latest updates and kernel 2.6.30.1 compiled on my own from kernel.org. I have also tried the provided 2.6.31-2-generic kernel, as well as the current Jaunty kernel (2.6.28-11-generic), but the results were the same:

Basically, I get my external USB drive detected, but I don't get the /dev files generated and therefore I cannot access my drive. There are many "device descriptor read/64, error"s and "device not accepting address %NUMBER%" errors followed by "unable to enumerate USB device on port 1" errors in dmesg:

[   87.256073] usb 1-1: new high speed USB device using ehci_hcd and address 5
[   87.389479] usb 1-1: New USB device found, idVendor=152d, idProduct=2329
[   87.389489] usb 1-1: New USB device strings: Mfr=1, Product=2, SerialNumber=5
[   87.389496] usb 1-1: Product: USB to ATA/ATAPI Bridge
[   87.389502] usb 1-1: Manufacturer: JMicron
[   87.389506] usb 1-1: SerialNumber: 13D107568FFF
[   87.389712] usb 1-1: configuration #1 chosen from 1 choice
[   87.650345] Initializing USB Mass Storage driver...
[   87.650566] scsi0 : SCSI emulation for USB Mass Storage devices
[   87.651035] usbcore: registered new interface driver usb-storage
[   87.653675] USB Mass Storage support registered.
[   87.681510] usb-storage: device found at 5
[   87.681518] usb-storage: waiting for device to settle before scanning
[   92.682146] scsi 0:0:0:0: Direct-Access     SAMSUNG  HD502IJ               PQ: 0 ANSI: 2 CCS
[   92.682401] usb-storage: device scan complete
[   92.689322] sd 0:0:0:0: [sda] 976773168 512-byte hardware sectors: (500 GB/465 GiB)
[   92.692523] sd 0:0:0:0: [sda] Write Protect is off
[   92.692529] sd 0:0:0:0: [sda] Mode Sense: 34 00 00 00
[   92.692532] sd 0:0:0:0: [sda] Assuming drive cache: write through
[   92.696598] sd 0:0:0:0: [sda] Assuming drive cache: write through
[   92.696605]  sda: sda1 sda2 sda3 sda4 < sda5 sda6 sda7 sda8 sda9 sda10 >
[   92.780431] sd 0:0:0:0: [sda] Attached SCSI disk
[   93.528106] usb 1-1: reset high speed USB device using ehci_hcd and address 5
[   93.732111] usb 1-1: device descriptor read/64, error -71
[   94.040092] usb 1-1: device descriptor read/64, error -71
[   94.256086] usb 1-1: reset high speed USB device using ehci_hcd and address 5
[   94.460062] usb 1-1: device descriptor read/64, error -71
[   94.768115] usb 1-1: device descriptor read/64, error -71
[   94.984117] usb 1-1: reset high speed USB device using ehci_hcd and address 5
[   95.448078] usb 1-1: device not accepting address 5, error -71
[   95.560070] usb 1-1: reset high speed USB device using ehci_hcd and address 5
[   96.024100] usb 1-1: device not accepting address 5, error -71
[   96.027749] usb 1-1: USB disconnect, address 5
[   96.144302] usb 1-1: new high speed USB device using ehci_hcd and address 6
[   96.374593] usb 1-1: device descriptor read/64, error -71
[   96.680062] usb 1-1: device descriptor read/64, error -71
[   96.896104] usb 1-1: new high speed USB device using ehci_hcd and address 7
[   97.100072] usb 1-1: device descriptor read/64, error -71
[   97.408095] usb 1-1: device descriptor read/64, error -71
[   97.624094] usb 1-1: new high speed USB device using ehci_hcd and address 8
[   98.088281] usb 1-1: device not accepting address 8, error -71
[   98.200090] usb 1-1: new high speed USB device using ehci_hcd and address 9
[   98.664071] usb 1-1: device not accepting address 9, error -71
[   98.664102] hub 1-0:1.0: unable to enumerate USB device on port 1

According to what Scott Zawalski said:
"Booted into Jaunty desktop Live CD worked fine, kernel 2.6.28-11"
I assume that the problem is not the kernel version.

I could not think of anything else than something was messed up in karmic koala, which prevents USB drives from working correctly. I just wonder what it is ... and more importantly, how to make it working again.