This appears to be a problem with the gradient palette. If the app crashes while the gradient palette is open, it remembers that that palette is open and tries to open it again on launch, which then crashes again. You can remove memorized palette information with the follow command line.
defaults delete com.pixelmatorteam.pixelmator PX2Palettes
defaults delete com.pixelmatorteam.pixelmator PX2Palettes
Statistics: Posted by jbruni — Yesterday 19:56:44