I've been having this really annoying thing happen the past few days, that has happened before but not as frequently. I create a project in Flash Builder, import some classes, and then on occasion it keeps erasing those classes. So then I get errors in a lot of my datatypes, have to go back through my document and retype the datatype so that it reimports the class.

What could be causing this? I know flash builder can be a bit buggy at times, but wasn't sure if someone else has had this problem and knows what might be causing it.