I've observed instability on my Macbook c2d with the Linus' latest
tree.  Symptom is that USB devices start behaving badly and the kernel
seems to be registering incorrect HID events; (ie. moving the mouse
causes odd keyboard events).  If I continue to attempt to use the
mouse, it results in a system freeze (and I don't see any kind of
backtrace in /var/log/kern.log).  To reproduce the problem, I just
need to be using the keyboard/mouse.  If I leave the system idle, the
problem does not seem to occur.  If I actively use the keyboard/mouse,
the problem can occur at any time; usually within 5-10 minutes.

In my particular case, I've got both a USB key/mouse pair on the
laptop and an external key/mouse pair plugged in via a hub.
Typically, it's the external mouse that exhibits badness first.

USB HID devices are definitely affected.  I have not tested USB block
devices.  Isochronous transfers to a USB headset appear to be
unaffected, but that's under minimal testing.

I've bisected down to commit 196705c9bbc03540429b0f7cf9ee35c2f928a534,
"USB: EHCI cpufreq fix"

Reverting the patch at the head of the tree makes the kernel stable again.

I've attached my kernel config file and a dmesg output

Cheers,
g.

-- 
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.
grant.likely@secretlab.ca
(403) 399-0195