CSS is frozen after starts an external program

[Chen Xue <xue@bio.aps.anl.gov>]

Hi,

We have an external program needs to be run in CSS GUI. I created a 
button to trigger this event, but I found it freezes CSS GUI after it 
runs. I have to use Ctrl-Z to stop this external program in terminal 
window, but it can't bring CSS alive.
Could someone help?

Thanks,

Chen