I submitted a crash log to Parallels and got the following response.
The problem is that Pokerstars is using an OpenGL technology, which is
not yet supported bu Parallels.
What you could try is: open the "Options" in Pokerstars and disable
"Animation". I'm not sure it will help, but it is possible to be the
reason of an error.
Unfortunately, I have a bonus to work off on Full Tilt and have not had a chance to play on Stars in a while to see if it works.