This happens for me on x86_64 as well.  It seems to not happen with nomodeset.

I confirm it solves the problem.
Thank you

Same problem for me.
I just added the nomodeset option to see if I get any improvement.

(In reply to comment #0)
> KMS is used. KDE doesn't use Desktop effect.
> I don't use any OpenGL applications. Only VirtualBox, an NXClient, some
> consoles, Firefox, Thunderbird.

Most likely something with KMS ... could we get output of dmesg command AFTER it crashes, please?

Unfortunately it is absolutely not possible to get any output, as system hangs completely, I can't even ping it after hang. As it was written in bug description - only hard reset.

Since this bugzilla report was filed, there have been several major updates in various components of the Xorg system, which may have resolved this issue. Users who have experienced this problem are encouraged to upgrade their system to the latest version of their packages. For packages from updates-testing repository you can use command

yum upgrade --enablerepo='*-updates-testing'

Alternatively, you can also try to test whether this bug is reproducible with the upcoming Fedora 12 distribution by downloading LiveMedia of F12 Beta available at http://alt.fedoraproject.org/pub/alt/nightly-composes/ . By using that you get all the latest packages without need to install anything on your computer. For more information on using LiveMedia take a look at https://fedoraproject.org/wiki/FedoraLiveCD .

Please, if you experience this problem on the up-to-date system, let us now in the comment for this bug, or whether the upgraded system works for you.

If you won't be able to reply in one month, I will have to close this bug as INSUFFICIENT_DATA. Thank you.

[This is a bulk message for all open Fedora Rawhide Xorg-related bugs. I'm adding myself to the CC list for each bug, so I'll see any comments you make after this and do my best to make sure every issue gets proper attention.]

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Fedora 11 changed to end-of-life (EOL) status on 2010-06-25. Fedora 11 is 
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I cannot reproduce the problem because I no longer own this hardware and I no longer use this Fedora version.