This is a strange one.
I have Raspbian installation which worked for weeks now. Keyboard is connected directly to raspi, other usb is connected to powered USB hub. There are just HDD and wifi dongle in hub. As I said, this was working nicely for a long time.
I did a backup of SD card and then installed raspbmc. I managed to work with wifi there, HDD was disconnected so that raspbmc does not change anything. Then I restored my previously working Raspbian. No hardwarew changes except unplugging and plugging HDD to the same port in USB hub.
Now when I start Raspbian, it gives me plenty of USB related errors like
usb 1-1.3: new high-speed USB device number 5 using dwc_otg
usb 1-1.3: New USB device found, idVendor=05e3, idProduct=0608
usb 1-1.3: New USB device strings: Mfr=0, Product=1, SerialNumber=0
usb 1-1.3: Product: USB2.0 Hub
hub 1-1.3:1.0: USB hub found
hub 1-1.3:1.0: 4 ports detected
hub 1-1.3:1.0: hub_port_status failed (err = -71)
hub 1-1.3:1.0: cannot reset port 2 (err = -71)
hub 1-1.3:1.0: cannot reset port 2 (err = -71)
hub 1-1.3:1.0: cannot reset port 2 (err = -71)
hub 1-1.3:1.0: cannot reset port 2 (err = -71)
hub 1-1.3:1.0: Cannot enable port 2. Maybe the USB cable is bad?
And these messages repeat without end.
(Of course I tried to connect to other computer, disk works)
lsusb does not show neither wifi, nor HDD. when I disconnect HDD, lsusb shows wifi and I can get network working.
Any idea what is happening here ? And how to resolve it ? This raspbian was running for many days without a reboot and all worked nicely.