sometimes the ESC key has proved useful in some situations, im not sure it would work with this but it is worth a shot.
also, I've learned that when sonar goes in to that state(white screening/freeze)
every once in a while if you click on the sonar icon in the task bar and minimize it/maximize it sonar can sometimes be recovered.
as well by clicking on the RED X as if to close the application, when presented with the option "do you want to close/wait for the application. simply choose wait.
these little things have been a little helpful, how helpful ?
id have to say ive been able to recover using these 3 options 30-40 % of the time.
its fair though to note, I don't crash often so these number don't reflect a user who is experiencing high count problems.
best of luck.
Charlie