Its likely project related. I think by a process of elimination you can find what is leading to the issue. Save a backup of the project before messing with it though. Then remove synths one by one till the problem goes away.
Another thing to try - save the project as a bundle then reopen it and try again. Saving as a bundle will remove any audiosnap elements.

Do you have 64 bit audio engine enabled?  I have a couple of plug-ins which suffer from this when bouncing down with 64 bit audio engine on.

Actually I have no audio plugins in the project at this time.  However, I turned off the 64 bit audio engine and that seems to have fixed it.  Strange though  because I use that in X2 with no issue, and also other X3 projects.  OH well, at least its solved!!
 
Thanks everyone for your help!

Marc2109
Actually I have no audio plugins in the project at this time.  However, I turned off the 64 bit audio engine and that seems to have fixed it.  Strange though  because I use that in X2 with no issue, and also other X3 projects.  OH well, at least its solved!!
 
Thanks everyone for your help!

Can we put [Solved] in the title?

Since SONAR uses the ASIO buffer size for offline rendering by default, make sure X2 and X3 are both set the same. I've not seen that kind of extremely slow rendering, but I have seen  bounce/export fail completely for some synths/FX when the buffer was too small.
 
There's a parameter in AUD.INI called BounceBuffSizeMsec that you can set to control the offline bounce buffer size. It's set to zero by default which tells SONAR to use the real-time ASIO buffer size for offline processing as well. Setting it to something between 20 and 200 (milliseconds) can improve offline bounce performance. Going bigger won't buy you much, and can cause issues with RAM limitations on export of very large projects. I've had mine at 20 for a long time with now without issues (aside from the bug with Bitbridge that causes an extra empty buffer of audio to be added to the front of the bounce, make the content late - not a problem with Jbridge).
 
There could also be an issue with some FX that's had a VST3 version substituted for VST2 in X3 - just a thought..
 
 EDIT: Oops missed the part about 64-bit engine. Still might be worth trying a larger bounce buffer. In any case, I imagine the Bakers would like to have a look at that project to see what the issue is.
 
 

Agree with resaving the project. Oft times the simple fact of physically changing the space on the HDD where the project is saved can make a world of difference.