A question first, have you been saving different projects in the same folder ?
This may cause unexpected things.
Your project is made of xml files, (files that can be edited with the notepad and are written in XML format, human readable).
So your project might be corrupted for now, but there ways to recover it hopefuly.
Make a zip file out of the content of the folder "Projects" and post it here using dropbox, or send it via mail to Ashleypoe@Scirra.com