Intermittent Failure after Upgrade

[Baz]

After the upgrade from "etch" to "lenny" several weeks ago, xorg is failing
at various instances. It can't be intentionally reproduced. The "error"
message indicated looking at the configuration first before filing a bug
report; however, it ended with "fatal server error lockup". I've reinstalled
xorg, xserver-xorg and all dependencies; but, it's still occurring. No error
messages in the xorg log. I'm running it on a Thinkpad Z60t.  Any
suggestions for a fix?
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