I'm assuming you have tried to open another project, or a
sample project, and that was ok.
If this is true, either you deleted / renamed the project's
.cpd file so RH could rebuild it (that's what it looks like as it
rebuilds) , or, you really need to do that.
In the project directory, delete the file that ends in .cpd.
YOu can rename it if that makes you feel better, but this is a
fairly safe process.
Then open the project, and let it finish the rebuild. On a
large project, this could take some time.
Good luck.