Comment 7 for bug 645211

Same / Similar issue - USB was working (Flash drives and USB Canon i965 printer) & then stopped working...
Found turning off ehci allowed both to work....

cd /sys/bus/pci/drivers/ehci_hcd/
sudo sh -c 'find ./ -name "0000:00:*" -print| sed "s/\.\///">unbind'
(echos unbind to the ehci device id)

lots of 'unable to enumerate' messages in dmesg;

[ 1744.750662] usb 1-1: new high speed USB device using ehci_hcd and address 42
[ 1744.880420] usb 1-1: device descriptor read/64, error -71
[ 1745.120056] usb 1-1: device descriptor read/64, error -71
[ 1745.350173] usb 1-1: new high speed USB device using ehci_hcd and address 43
[ 1745.480055] usb 1-1: device descriptor read/64, error -71
[ 1745.723513] usb 1-1: device descriptor read/64, error -71
[ 1745.950062] usb 1-1: new high speed USB device using ehci_hcd and address 44
[ 1746.370083] usb 1-1: device not accepting address 44, error -71
[ 1746.490094] usb 1-1: new high speed USB device using ehci_hcd and address 45
[ 1746.910045] usb 1-1: device not accepting address 45, error -71
[ 1747.030065] usb 1-2: new high speed USB device using ehci_hcd and address 46
[ 1747.160070] usb 1-2: device descriptor read/64, error -71
[ 1747.407157] usb 1-2: device descriptor read/64, error -71
[ 1747.630059] usb 1-2: new high speed USB device using ehci_hcd and address 47
[ 1747.760053] usb 1-2: device descriptor read/64, error -71
[ 1748.000055] usb 1-2: device descriptor read/64, error -71
[ 1748.230102] usb 1-2: new high speed USB device using ehci_hcd and address 48
[ 1748.650063] usb 1-2: device not accepting address 48, error -71
[ 1748.770060] usb 1-2: new high speed USB device using ehci_hcd and address 49
[ 1749.190037] usb 1-2: device not accepting address 49, error -71
[ 1749.190074] hub 1-0:1.0: unable to enumerate USB device on port 2
[ 1749.370122] usb 1-3: new high speed USB device using ehci_hcd and address 50
[ 1749.500063] usb 1-3: device descriptor read/64, error -71
[ 1749.740065] usb 1-3: device descriptor read/64, error -71
[ 1749.973733] usb 1-3: new high speed USB device using ehci_hcd and address 51
[ 1750.100057] usb 1-3: device descriptor read/64, error -71
[ 1750.340061] usb 1-3: device descriptor read/64, error -71
[ 1750.570103] usb 1-3: new high speed USB device using ehci_hcd and address 52
[ 1750.990070] usb 1-3: device not accepting address 52, error -71
[ 1751.110118] usb 1-3: new high speed USB device using ehci_hcd and address 53
[ 1751.531122] usb 1-3: device not accepting address 53, error -71
[ 1751.531520] hub 1-0:1.0: unable to enumerate USB device on port 3
[ 1751.710204] usb 1-4: new high speed USB device using ehci_hcd and address 54
[ 1751.843296] usb 1-4: device descriptor read/64, error -71
[ 1752.090084] usb 1-4: device descriptor read/64, error -71
[ 1752.320105] usb 1-4: new high speed USB device using ehci_hcd and address 55
[ 1752.460086] usb 1-4: device descriptor read/64, error -71
[ 1752.690515] usb 1-4: device descriptor read/64, error -71
[ 1752.920088] usb 1-4: new high speed USB device using ehci_hcd and address 56
[ 1753.340041] usb 1-4: device not accepting address 56, error -71
[ 1753.460069] usb 1-4: new high speed USB device using ehci_hcd and address 57
[ 1753.880039] usb 1-4: device not accepting address 57, error -71
[ 1753.880078] hub 1-0:1.0: unable to enumerate USB device on port 4

uname -a:
Linux fitsserver 2.6.32-24-server #38-Ubuntu SMP Mon Jul 5 10:29:32 UTC 2010 x86_64 GNU/Linux
Intel atom Dual core

David