That's the same set-up I'm using. Do you get this problem
often? Is it
reproducible? Is there a particular thing that you are doing when this
happens?
Only seen it once so far, at the time I was running my i386 install of
firefox (I have 32/64 versions installed mainly for flash) and had a
couple of flash pages up and running at the same time. I noticed that
my browser, and evolution became unresponsive at the same time and I had
to force quit them.
I'm trying to push my firefox/flash again to see if it barfs.