You may see one or more of the following problems:
You could you try to retrieve the project by taking a previous revision using Tortoise SVN (download is free).
Use the following command:
svn co -r TheNumberOfRevision http:/ /your_server/tis_repository/yourproject
Once you have checked out the revision, you can:
Create a new project in the Talend Administrator.
In the Studio, open this new project.
Choose Import items and select all to browse your checked out project.
This will help you retrieve your corrupted project at a previous state.