It is rare that I cannot open a project, even in safe mode after disabling all plugins, but it has happened.
The auto-save version as well as all recent asset versions will not open.  
It says "may be incompatible with this version of sonar or is damaged".
 
Anyone know what my options are?
 
I do have the project safely backed up, I'm just hoping to not lose 3 hours worth of a clients work.
It would mark the second time since opening my studio in 2006 that I had to ask a client to redo a session at my expense.
The project did not offer any signs that there was a problem.  We worked on it for a few hours, saved it no problem- ne'er to open again!
 

Wow, I never had this problem and would like to know how it works out for you!

Hopefully you'll find a solution...worst case is that it's a hardware problem, like losing sectors on a hard drive. I don't trust hard drives, so I back up to a different hard drive than the original project. You might try chkdisk and see if it finds anything.
 
Not sure what the three hours of work involved, but if it was recording, then the audio is somewhere in your project folder. If it was tweaks to mixes and stuff, hopefully there's a saved Mix Recall file.

BlixYZ
The auto-save version as well as all recent asset versions will not open.  
It says "may be incompatible with this version of sonar or is damaged".

.asset files are not Cakewalk project files.
If versioning is setup use File > Revert from the menu to load previous versions of the project.

Can't help you but I also have that problem with a project, the thread is here: 
http://forum.cakewalk.com/Sonar-scrashes-on-projectload-m3384370.aspx
 
I have started over on the project by using the the LE version with drag and drop. But I lost all the settings from pro version.

I am with Graig on the bad sectors on the hard drive. If I was having issues like this, As well as running chkdsk, I would be looking at the Windows system event viewer (Start run - eventvwr.msc) and finding any disk issues (using the filter current log to display only disk events).  

You could also run a disk tool that checks the S.M.A.R.T. information.  This will show the likelihood that a drive is about to fail (I use a tool called CrystalDisk info)

I have this problem too.  it usually happens when a vst device froze sonar at the same time sonar was busy doing a auto safe. I've disabled auto safe. Now I save the project  manualy white a timestamp in the  name.
Í'm afraid your project is ruined.

Do you have any older versions of Sonar installed?
I had this occur once in Platinum, I was able to open the project in X3. X3 warned that it was saved in a newer version, but I let X3 open it anyway. I then saved a new copy, and Plat opened it fine.
 
 

jatoth
Do you have any older versions of Sonar installed?
I had this occur once in Platinum, I was able to open the project in X3. X3 warned that it was saved in a newer version, but I let X3 open it anyway. I then saved a new copy, and Plat opened it fine.
 
 

That´s the point I thought also first of.
I managed to open some elder projects which was not possible via Splat
using Sonar 8.5 (64 bit).and X1.
There I bounced the tracks and imported them to a new Splat project.

In the past if a project wont open CW has asked that it be sent to them and they can open it. Contact CW about this.