One of a few options often takes care of the stuck issue.
1) Manually delete the shadow files from the pref > General > Manually Delete tab if you are using them. Allow them to regenerate after opening project or if you can, don't use them
2) Leave it sit at the 80% for several hours, often it may open
3) Look to see if you have auto save project selected in pref > Project and surf to directory and see if a older saved version works.
Jeff