I click reset performance data and FlashBuilder beachballs (I'm on OS X.) I'm not sure if it will recover- I've given it 20 minutes before and it was still frozen up. Sometimes I can successfully click it, but then clicking capture performance will kill it.
What can I do to figure this out? I've looked at the workspace logs and there's absolutely nothing printed out when it bombs.
You can try reducing the amount of time that you are taking samples. Maybe
add a button or some code that calls the Sampler API to clear samples until
you're ready to examine whatever it is your are interested in.