I'm having troubles connecting my external usb harddrive.
After disconnecting and connecting it sometimes works but most of the time I see this message in the log:

[ 393.364074] usb 1-1: new high speed USB device using ehci_hcd and address 17
[ 393.516104] hub 1-0:1.0: unable to enumerate USB device on port 1

Anybody any idea on how to solve this?