hiii....
im tried to mount my usb but when i type a command :
[root@fedora /]# tail -s 3 -f /var/log/messages

it appear....

Mar 9 22:15:45 fedora kernel: usb 5-5: new high speed USB device using ehci_hcd and address 3
Mar 9 22:15:48 fedora kernel: usb 5-5: device descriptor read/64, error -110
Mar 9 22:16:03 fedora kernel: usb 5-5: device descriptor read/64, error -110
Mar 9 22:16:03 fedora kernel: usb 5-5: new high speed USB device using ehci_hcd and address 4
Mar 9 22:16:07 fedora kernel: usb 5-5: device descriptor read/64, error -110
Mar 9 22:16:22 fedora kernel: usb 5-5: device descriptor read/64, error -110
Mar 9 22:16:22 fedora kernel: usb 5-5: new high speed USB device using ehci_hcd and address 5
Mar 9 22:16:32 fedora kernel: usb 5-5: device not accepting address 5, error -110
Mar 9 22:16:32 fedora kernel: usb 5-5: new high speed USB device using ehci_hcd and address 6
Mar 9 22:16:43 fedora kernel: usb 5-5: device not accepting address 6, error -110

Normally you just plug it in and turn it on for a USB hard drive in Fedora and a window shows up asking if you want to open it, if you select "no" it will not be mounted. If this is a USB pen drive, it may need to be re-formatted.