I asked this question in SuperUser one hour ago, then I know this community so I moved the question here...

I've been running Ubuntu 10.10 in a physical x86-64 machine. Today Update Manager reminded me that there are some updates to install and I confirmed the action. I should had read the update list but I didn't. I can only remember there is an update about cups. After the upgrading, Update Manager requires a restart and I confirmed too. But after the restart, the computer can't start up. There are errors in the console.

Begin: Running /scripts/init-premount ... done. 
Begin: Mounting root file system ... 
Begin: Running /scripts/local-top ... done. 
[xxx]usb 1-8: new high speed USB device using ehci_hcd and address 3 
[xxx]usb 2-1: new full speed USB device using ohci_hcd and address 2 
[xxx]hub 2-1:1.0: USB hub found [xxx]hub 2-1:1.0: 4 ports detected 
[xxx]usb 2-1.1: new low speed USB device using ohci_hcd and address 3 
Gave up waiting for root device. Common probles:
     - Boot args (cat /proc/cmdline)
        - Check rootdelay=(did the system wait long enough)
        - Check root= (did the system wait for the right device?)
     - Missing modules (cat /proc/modules; ls /dev) 
FATAL: Could not load /lib/modules/2.6.35-22-generic/modules.dep: No such file or directory
FATAL: Could not load /lib/modules/2.6.35-22-generic/modules.dep: No such file or directory ALERT! /dev/sda1 does not exist. Dropping to a shell! 
BusyBox v1.15.3 (Ubuntu 1:1.15.3-1ubuntu5) built-in shell(ash) 
Enter 'help' for a list of built-in commands. 
(initramfs)[cursor is here]

At the moment, I can't input anything in the console. The keyboard doesn't work at all. What's wrong? How can I check boot args or "root=" as suggested? How can I fix this issue? Thanks.

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PS1: the /dev/sda1 is type ext4 (rw,nosuid,nodev)

PS2: the /dev/sda1 can be mounted and accessed successfully under SUSE 11 SP1 x64.

PS3: From this link, I think the keyboard doesn't work because the USB driver is not loaded at that time.