random keystrokes ignored on console

Sometimes, when I type in the console, about 40% of the keystrokes are ignored.
If I type (for example) "startx" and hit enter, I'll see "sart" or somesuch and
the command fails. In that same case, typing "sttartxx" and enter probably
would have worked, with "startx" being run. The enter key is also affected, so
maybe I'd have had to hit it twice. This is frustrating, obviously. This
- does not seem to be related to system temperature,
- does not happen in X,
- doesn't seem to be happening consistently,
- and affects logging in (username & password) too.

This is on a new ThinkPad running Debian Lenny/Sid amd64. I thought this
problem could be hardware-related, so I ran the hardware tests available on the
Rescue & Recovery disc included with the laptop. Two tests failed:
System Board: USB Port Test - Abnormal Exit
SMBIOS: Standards Test - Failed
but they don't seem related to the problem.

Any thoughts? Thanks.

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