It could be that the project is corrupt or something you (or Logic) does at a certain point of editing is causing Logic to crash.
Difficult to know what to suggest unless you can provide more details about version numbers and what function you're performing at the time of the crash.
You may not want to read this... but here goes:
It's vital (with any application) that you save on a regular basis. Logic creates backup project files every time you hit that magical shortcut:
Let us know more details (Logic version, OSX version, Mac, audio interface, etc) and we'll do our best to help.