This has happened maybe 12-15 times since I upgraded (I upgraded the day X3e came out).  It's obviously quite annoying because it's hanging on save, so I lose everything I've done since last save.  I save every 3-5 minutes or so, it's not the end of the world but pretty annoying.  I don't have autosave turned on so I don't know if it would hang during autosave.
 
Can't pinpoint any specific pattern or behavior I'm doing before the hang.  Working in my standard template, using a couple of standard plugins: omnisphere, kontakt, 3 or 4 sonitus fx.  I've let it sit here for up to 30 minutes hoping it will "un-hang" but it never does so I force reboot.
 
Here's the event log, anyone know how to read this thingy??  Any clues?
 
P.S. This never happened with X3d for me, just since X3e.
 
Log Name:      Application
Source:        Application Hang
Date:          3/26/2014 8:58:33 AM
Event ID:      1002
Task Category: (101)
Level:         Error
Keywords:      Classic
User:          N/A
Computer:      Booger
Description:
The program SONARPDR.exe version 20.0.5.352 stopped interacting with Windows and was closed. To see if more information about the problem is available, check the problem history in the Action Center control panel.
 Process ID: 53f0
 Start Time: 01cf48f9104e509b
 Termination Time: 49
 Application Path: C:\Program Files\Cakewalk\SONAR X3 Producer\SONARPDR.exe
 Report Id: 79c96b77-b4ff-11e3-ad6e-002590e54cf1
Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
  <System>
    <Provider Name="Application Hang" />
    <EventID Qualifiers="0">1002</EventID>
    <Level>2</Level>
    <Task>101</Task>
    <Keywords>0x80000000000000</Keywords>
    <TimeCreated SystemTime="2014-03-26T15:58:33.000000000Z" />
    <EventRecordID>5583</EventRecordID>
    <Channel>Application</Channel>
    <Computer>Booger</Computer>
    <Security />
  </System>
  <EventData>
    <Data>SONARPDR.exe</Data>
    <Data>20.0.5.352</Data>
    <Data>53f0</Data>
    <Data>01cf48f9104e509b</Data>
    <Data>49</Data>
    <Data>C:\Program Files\Cakewalk\SONAR X3 Producer\SONARPDR.exe</Data>
    <Data>79c96b77-b4ff-11e3-ad6e-002590e54cf1</Data>
    <Binary>55006E006B006E006F0077006E0000000000</Binary>
  </EventData>
</Event>

Try emptying your Cakewalk picture cache once. See if that does anything.

Will do.  Only 3,600 picture files that's nothing.... I've had that sucker up to 30k or 40k before.  Unfortunately no way to recreate the hang, but so far I've been working for 30 minutes without it hanging on save...

Couple quick questions. Are you explicitly running X3 as administrator? Also check background processes (especially virus checkers) that may be intercepting the write on you to analyze it. The only other thing that comes to mind offhand is the I/O buffer size, I had to set mine to 512KB for larger projects to save (Advanced Mode: Preferences->Audio->Synch and Caching). This did not make the program hang, but gave a pop-up window of "General Program Error" preventing the save until they were bumped up.