I know the x1600 has issues getting full resolution and support for CI/QE but this is also discussed in the forum. As for the updates... it never hurts to do a forced loading at boot of the Extensions folder (-f). I fear that this is a graphics issue more than anything... so after making sure your kexts and bundles for getting the x1600 working in 10.5.2 backed up, remove them from the /System/Library/Extensions/ folder and do a forced boot (-f) to recreate the .mkext file. now look into the issue for fixing the graphics via the other thread.

Let me know if this stops the freeze because at the moment thats the only thing that is coming to my mind to be the cause.

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