I'm working on a fairly large project (25 tracks at about 3 hours in length, lots of Waves plug-ins, lots of Melodyne usage, etc.) and every time I try to bounce the project down, X3 crashes.  All I do is select the 3ish hours of audio, go to the export screen, and choose the following options:
 
Source Category: Entire Mix
Channel Format: Stereo
Sample Rate: 48000
Bit Depth: 24
Ditheirng: None
Mix Enables: All selected except "Audible Bounce" and "Live Input"
 
I've tried both Wave and AIFF file formats, but if I use the above settings, when I hit "Export" X3 starts to do the bounce and then approximately 2 seconds later it crashes with the error "SONARPDR.EXE has stopped working.  A problem caused the program to stop working correctly.  Windows will close the program and notify you if a solution is available".  Before I started any mixing/editing, I did a bounce of the exact same selection of audio and it worked just fine.  The only way I can get it to work is if I deselect "Fast Bounce" and choose "Wave" as my file format (AIFF still crashes X3 even without doing a fast bounce).  But even then, I end up with blips in the bounced audio where small portions of the file are silent which were not present in the original project (which is definitely unacceptable). I'd like to try it in X2 but I can't (or at least it wouldn't be a fair comparison) because I used the integrated Melodyne in X3 quite a bit on this project.  If X3 does crash, when I open it back up it says: "There are no audio devices for the current driver model on your system.  Please go to Edit | Preferences | Audio | Playback and Recording and choose a different driver model".  It won't fully recover until I either reset my audio device (VS-100) or reset my computer.  I should also mention that the version of X3 I'm currently running is Sonar X3 Producer (X3b build 216) - x64.
 
I don't think it's my computer.  I'm using a Dell Studio XPS 9100 running 64-bit Windows 8 Pro, i7 CPU @ 3.20GHz, 12GB RAM which should be able to handle this.  I've also e-mailed Cakewalk tech support about this but haven't heard any sort of response for at least a week, if not more.
 
So far, I have had mostly problems with X3 (plug-in GUIs not drawing correctly, plug-ins missing in the plug-in manager, X3 crashing a lot, etc.) and I'm hoping that X3c resolves these issues.

What kind of digits are you seeing for CPU usage playing the project?
"Lots of Melodyne and Waves" makes me think you should bounce them to tracks or freeze them before exporting.
They are resource hogs, and Melodyne is also a very, very complicated. I never leave an active instance of Melodyne in the project when I close it. I've experienced many kinds of hiccups when forgetting that.

Bouncing tracks/freezing is a very good idea, I should have thought of that!  I don't know about the CPU usage but I'll check that when I get home later.  I'll also try freezing the tracks.  Thanks for the suggestion!

This happend to me aswell with a small project,crashed when exporting.
Peace

Another option is to select "E" on your keyboard. This will bypass your FX. Try to bounce your project with your FX bypassed and see if it crashes.

Lost a whole project today, now the project is corrupt weeks of work gone in one hit. The same happened to me as you. I've sent numerous problem reports today as I've tried to get the project to work again.

The common denominator melodyne First I got a hard drive full fault when trying to save after making melodyne corrections..... I actually have 500 meg spare. Then whilst bouncing .... Boom it went.

Thankfully I have a backup but I still have a full days work gone.

i have the same problem a few times , for me it was melodyne regionFx
try to bounce your melodyne regionFX `s to clip`S first. and than make your bounce to mix..
i also have files over 300 mb most it is one track who makes the problem
when i delite my picturecash and try open the song 2-3 times mostly i can open the broken project. than i have to figure out which track does make  the problem,
i try to bounce every track to clip and the brocken track makes the crash. so i have to delite the broken track. but sometimes i cant delite the broken track ..