Description:
When closing the lid of my HP Compaq 6720s the kernel panics in most cases.
This happens both in the 32 and 64 bit versions and began sometime last week, whether X is started, or even installed, is irrelevant.
I tried downgrading the kernel to 2.6.28.8, but it still happened.
The only thing I found to work is to boot with acpi=off, but this is a pretty bad alternative.
Even with a completely fresh FTP install of Arch it dies.

Additional info:
kernel26-2.6.29.2-1
I tried to get a hold of the kernel panic message, but it changes every time, and sometimes I get a full 1024x768 screen worth of text and sometimes I only get a few lines.

Steps to reproduce:
Start Arch normally on an HP Compaq 6720s.
Close the lid of the laptop. The screen doesn't go blank as usual.
When opening again, X is completely frozen and when X is not started you might see some lines from a kernel panic.
In rare cases the system does not crash, but closing the lid again quickly remedies this situation.