I just posted a tech support request for this, but I thought I'd mirror it here with a bit more information that I couldn't fit in the description field.
 
I just upgraded from SONAR X2 Producer to X3 Producer. When I try to open a particular existing project, the app hangs with the blue circle cursor. The first couple days, the file would open after five to ten minutes, seeming to take longer every time I opened the file. Now the file no longer opens at all, at least after 30 minutes.
 
Looking at automated backup files, the .cwp files seem much larger than I would expect. The oldest X2 backup is 10MB. The first post-X3 backup is 17MB. The next two are 32MB. The current size is 60MB. I did a small amount of recording in-between, but no more than a dozen clips totalling 5 minutes tops, probably much less.
 
During the hang, the SONARPDR.exe process uses 100% of a single CPU core. Once the file opens (when it used to open), everything seems to work normally.
 
The same phenomenon happens when I attempt to open the file now with X2 (although the file now has some X3-specific plugins in use). But the problem did not appear until I installed X3. Other projects--that I have never saved with X3--still open normally under X2 and X3. I can open the backups of the problem project with both X2 and X3, although they take longer than I would expect.
 
I have tried rebooting, running X3 as administrator, and running Windows Update with no luck.
 
Machine specs:
* Windows 8 Pro x64
* Four CPU cores
* 8GB RAM
 
Digital audio gear:
* Delta 1010
* Line 6 POD XT
* Oxygen 61
 
When I attempt to open the problem file, a series of Windows Event Log messages appear in the Applications log:
 
msiexec (3984) Instance: The database engine (6.02.9200.0000) is starting a new instance (0).
-----------
msiexec (3984) Instance: The database engine started a new instance (0). (Time=0 seconds)
Internal Timing Sequence: [1] 0.000, [2] 0.000, [3] 0.000, [4] 0.000, [5] 0.000, [6] 0.000, [7] 0.000, [8] 0.000, [9] 0.000, [10] 0.000.
-----------
msiexec (3984) Instance: The database engine attached a database (1, C:\ProgramData\Microsoft\Windows\AppRepository\PackageRepository.edb). (Time=0 seconds)
Internal Timing Sequence: [1] 0.000, [2] 0.000, [3] 0.000, [4] 0.000, [5] 0.000, [6] 0.000, [7] 0.000, [8] 0.000, [9] 0.000, [10] 0.000, [11] 0.000, [12] 0.000.
Saved Cache: 1
-----------
msiexec (3984) Instance: The database engine detached a database (1, C:\ProgramData\Microsoft\Windows\AppRepository\PackageRepository.edb). (Time=0 seconds)
Internal Timing Sequence: [1] 0.000, [2] 0.000, [3] 0.000, [4] 0.000, [5] 0.000, [6] 0.000, [7] 0.000, [8] 0.000, [9] 0.000, [10] 0.016, [11] 0.000, [12] 0.000.
Revived Cache: 0
-----------
msiexec (3984) Instance: The database engine stopped the instance (0).
Dirty Shutdown: 0
Internal Timing Sequence: [1] 0.000, [2] 0.000, [3] 0.000, [4] 0.000, [5] 0.000, [6] 0.000, [7] 0.000, [8] 0.000, [9] 0.000, [10] 0.000, [11] 0.000, [12] 0.000, [13] 0.000, [14] 0.000, [15] 0.000.
Fault bucket , type 0
-----------
Event Name: AppHangTransient
Response: Not available
Cab Id: 0
Problem signature:
P1: SONARPDR.exe
P2: 20.0.1.211
P3: 5243f5ad
P4: unknown
P5: unknown
P6: unknown
P7: unknown
P8:
P9:
P10:
Attached files:
These files may be available here:

Analysis symbol:
Rechecking for solution: 0
Report Id: e53c732b-2afe-11e3-bea8-485b39caaf65
Report Status: 2049
Hashed bucket:
 

I don't think the event viewer is very useful here. 
Are you using Melodyne ARA in this project? If not I don't think this is X3 specific. Any audio snap in the project? You may need to upload a version of the project for us to look at.

Yes, the first thing I did after opening the project in X3 is switch some clips from V-Vocal to Melodyne.  (The latter is a clear improvement sonically.)  I'm happy to upload the project and its backups if it would help.  Where/how do I do so?
 
Thanks for the quick response.

Sorry, missed the question about audio snap:  Yes, I think there are some audio snapped clips in the projects.  I bounced most audio snapped clips to a single clip that I transformed to a groove clip, then deleted the original tracks.  (All the current recording are guide tracks, which is why I'm not completely flipping out.)  But I think there is at least one audio snapped clip in the project.  I can't verify this because I can't open the project.
 

Other folks report problems with VST scanning, so I removed all VST scanning paths.  The project still fails to open while consuming 100% of a single CPU core.

I suggest uploading the project using yousendit or some other file sharing service. You can use Google Drive as well. You can post a link here or PM me the link.

Project file is available here:
 
 [Edit:  Because I'm newly registered to the forum, the system won't let me PM or post links, so I'll try to strip off the https:// part.]
 
docs.google.com/file/d/0BxcWsc4IvzckLXhpLUxXbW1vSFU/edit?usp=sharing

No links until 25 posts

Fair enough.  At least from my browser, removing the leading "https://" made the link visible.
 
Some additional info:
* The problem project opens after about an hour of the busy cursor.
* Once open, I can no longer save as a "Normal" or "Template" project.  After about a minute, I get a "General Error" message box.
* When I try to save as as a bundle, I get a message box saying that projects with AudioSnap data cannot be saved as a template.  This confirms there is indeed audiosnap data in the project.
* After deleting one track with a groove clip (but no audio snap), I can successfully save, but now the .cwp files size nearly doubles from 60MB to 117MB.
 
[Edit:  Added a bullet and fixed typo.]

I looked at your file. Its taking long to load and the file size is large because it contains millions (literally) of audio snap markers in it. There appear to be some clips with 524288 stored markers. I can't get a fuller picture since you only uploaded the CWP file and no audio but I suspect something has gone corrupt with the audiosnap markers in project. I suggest getting rid of the audio snap and saving the project. 
 
If I remember right, a quick way to do this is to turn off audio snap on all affected clips and then try and save the project as a bundle file. Then you should get a prompt telling you that you need to discard the audiosnap markers. Choose yes to that and the file will get saved without the markers. Now load it back from the bundle and save it as a project file again. The size should be small again and it should load quickly.
 
This problem is not specific to X3.