Kernel profiling on a dual xeon with HTT leads to wedge?

I tried to turn on high precision kernel profiling on a dual Xeon box with
HTT (so four logical processors) at work today.  Unfortunately, whenever I
do so, it seems to wedge hard within a few seconds.  I can typically hit
enter on the serial console maybe 4-6 times before it hangs pretty solidly
(serial break doesn't work).  I don't remember having this problem before,
but when I backed the kernel out fo Feb 7, Jan 1, Dec 1, and Nov 1 the
problem remained.  I'm wondering if maybe I had HTT off on the box
previously, but can't turn it off remotely currently so can't try that
now.  Does anyone else have kernel profilng working with >2
physical/logical processors?

Robert N M Watson