Last week I was battling a deadline when my scrivener project suddenly collapsed and didn’t regain consciousness. In the project I had several pdf and word files in the research map. In the text I had put several pdf cuttings as illustrations. Just after I copied a powerpoint drawing into the text of the project, the project collapsed. A tried to restart it again, but after many anxious moments of waiting I had to force close the program. 
Luckily I had reported a draft the day before and was able to finish my paper on the basis of that. 
Maybe a known issue for experienced scrivener users, but I thought it sensible to post a warning. Lesson learned: be carefull with powerpoint. It might also be caused by the number of pdf bits I put in the project, but I think it is the powerpoint drawing which caused the problem.
I am not at all familiar with PowerPoint; what is the file extension for the drawing format? It might be that the PowerPoint Drawing file extension looks like something else to Scrivener and it is attempting to read it as something it shouldn’t. Also, if it doesn’t have any extension at all, Scrivener will probably try to read it like a text file which yes, would take a rather long time and cause the application to appear as though it had frozen. Scivener doesn’t actually have a clue on what to do with PowerPoint files of any kind. It should have just rejected the file as unknown, but again if the extension looks like something else, or it has no extension at all (should always use extensions in OS X), it might have slipped through the net.
And you are right, the “no file extension” issue is a known thing, though it usually comes up with people trying to drag Word files without “.doc” into Scrivener and ending up with a file full of gibberish.
The rest of this message contains some instructions for project recovery that should be considered “moderately advanced.” If you are not comfortable proceeding, or have all of the data you need already, feel free to skip it.
If you still have the project file around, make a duplicate copy of it, and then on the copy right-click and choose “Show package contents…” This will reveal the files that make up your project. Scroll down, you should see a long list of numbered RTFD files. Since the PowerPoint file was your more recently added thing, it will probably be down toward the bottom of the list. Look for an RTFD file with a suspiciously large file size, and utilise QuickLook (if on Leopard) to check for RTFD files full of gibberish. When you locate the file, delete it using the Finder. Now close the window and double-click on the altered project file. It should open up quickly, and you can delete the (now empty) “Powerpoint file”. This procedure should be safe, though it is not recommended for ordinary usage. 
Your project file is already messed up though, and if you work on a duplicate you should be able to get yourself to a spot where you can at least open the project again. If you can, I would recommend creating a new project and dragging everything in the Binder of the fixed project over to the new empty project. Everything with the exception of labels and status will be copied over. Even snapshots, notes, keywords, and so forth.
Great tip for the recovery. Unfortunately I had deleted the project already, but this clear explanation I’ll keep in mind for another emergency situation. Doesn’t look overly complicated, especially with the step by step you’ve given. Thanks!