Drape is notorious for having a hard time with large models, and models with many very small faces. When I use the drape tool, I always save before draping, and I often only drape small amounts at a time. Then I save after each drape operation. Often you will find one area of the model that will crash. Sometimes I will hand drape a few segments of lines on the really difficult models.
Sorry about the crashes, hope that helps.
Do you by chance have a model you can share that causes problems? Or even just a screenshot of it, just so I can have a better understanding of the complexity of the model you are talking about?
Chris