Have you checked whether the computer your using meets CorelDraw X6's System Requirements?
Other thing is are you keeping an eye on temperature of CPU especially if it's working really hard (Just like a cars engine that runs at high end of revs eventually cooling will not be able to be enough to keep it at proper operating temperature), therefore shutdown.
OR it's time to clean fans on CPU and or Case Fans etc.
Answers & Comments
Have you checked whether the computer your using meets CorelDraw X6's System Requirements?
Other thing is are you keeping an eye on temperature of CPU especially if it's working really hard (Just like a cars engine that runs at high end of revs eventually cooling will not be able to be enough to keep it at proper operating temperature), therefore shutdown.
OR it's time to clean fans on CPU and or Case Fans etc.
All the best anyway.