And I've also tried opening up a new project and importing the old one into it - this dosen't work either
Have you explored the AutoSaves? They will be where you have located them in the Scratch Disks location, in the AutoSave folder for that Project. Hope that one of them works.
Also note that AutoSaves are FIFO, so do not just go by the last numeral in the AutoSaves. The most recent might be, say # 3, and not # 5.
What version of PP was this project started on? What version are you using now?
If the AutoSaves produce the same problem, you might try "hiding" the Assets (in case one, or more, is corrupt) from PrPro.
Exactly how you do this, will depend on where you have your Assets located. Let's keep it simple, and for this example, assume that you have all of your Video in a folder under the Project's root folder, say E:\[Project Name]\Video, and then your Still Images in E:\[Project Name]\Stills. Change the folders' names to \\Video_new and \\Stills_new.
Open the Project. Do you get "Where is file ____ ?" If so, that is a good sign. PrPro uses absolute Paths for the links to Assets, and you have broken those links. You should get a Finder dialog, where you can navigate to the new location. There, once PrPro finds the first file, in that folder, that has a broken link, it will search that folder and link to all other Assets in the Project, that reside there. For separate folders, repeat the process, when queried about a broken link.
Now, since PrPro will search each such folder, relinking, once the first file has been identified, if you have, say one corrupt Video file, the Project might hang when trying to link to that. If this happens, I would Exit, and go to the Video (or other folder), and break that into parts, say \\Video_new_01, \\Video_new_02, etc., and Move Video files into those. Then, Open that Project again, and note which folder PrPro hangs on. That will tell you the group of Videos, that has the corrupt one(s).
Note: NEVER Save over your original Project files! Only use Save_As, and increment the Project's name. This is very important if you choose to Skip, or Offline any of your Assets, at "Where is file ____ ?" If you do Save over the original, then you will have to manually link each Asset.
I've been experiencing corrupted projects too. I can't see to hide enough assets from the project to allow it to load, so I don't know that it has anything to do with assets. I mean previous saves load and they don't involve any more assets, just further editing of same assets.
So I'm getting into a habit of incrementing the project file name more regularly, until this is hopefully addressed in an update... but is there anything to be done here other than reverting back to an old save and losing hours of work (thankfully hours and not days)?
It would really help (Adobe!) to see a more detailed error message than "The project could not be loaded, it may be damaged or contain outdated elements."
I doubt it is outdated elements, assets have not changed. But is there a "debug" mode where I can extract more information from this?
Also, I can't say at this point I'm 100% certain but I'd wager PPro has been corrupting once functional saves without me telling it to re-save.
I've closed a project... opened a project... NOT saved that project, tried to open it again only to see the above error message. I'm 90% certain that's what has happened twice to me. Will post again if I can confirm it now that I'm paying attention for it. Just sharing in case anyone else has experienced (or think they have experienced) the same.
I really do hope Adobe can iterate quickly on PPro CS6... the Creative Cloud biz model incentivises app stability over brochure feature list I hope... certainly the reason I abandoned SONY Vegas was that they kept adding features yet I never stopped experiencing crashes (across multiple projects on multiple computers).
As I'm building up a complex project in PPro I'm seeing similar fundamental problems... certainly PPro isn't crashing as much (although it does crash). But I'll never care about any "new" feature in any future release as much as I will stability and the integrety of project saves.
Update: If anyone wants to inspect the project, I've confirmed it still will NOT load regardless of assets... I disconnected my asset drive and the project gives the same error when I try open it. Here it is: http://gordonmcdowell.com/gord-tools/TR2012-177-Bad.prproj ...I'll submit a proper bug report (I guess) once I've had a few days to try confirm PPro is actually corrupting projects without me clicking Save. (Which would help me describe how this project became corrupted... with or without me clicking Save.)
Did you try to import the entire Project or each individual sequence? If you did not try 1 sequence then delete your media cache files in your media cache directory and then try and import just 1 sequence.