Comment 51 for bug 204603

Created an attachment (id=17403)
debug register I/O

This looks very similar to #15168...

Can you try this patch? Also, please add a section like this to your
Section "ServerFlags"
        Option "Log" "sync"

Hopefully the log syncing will give us a useful log of where the hang happens.
It would be best to start your X session by ssh'ing into the laptop and running X with the -verbose option, that way even if the log isn't preserved you'll see what's going on.