I'm having lots of the dreaded 'audio engine has stopped working' messages in X3e. 
So... what diagnostics steps should I take to track down the problem?
 
What I know so far:
- it will record happily for short bursts
- hard drive thrashes when it stops
- happens for tracks with only 2x audio tracks and no soft synths
 
System wise:
- Roland Quad Capture with latest drives
- Windows 8.1 fully patched with an SSD boot drive
- Plenty of CPU power (i7 4790, 16Gb RAM)
 
This has only started happened recently. My old motherboard died so I had to replace a lot of hardware but did not re-install windows. This is partly time due to the number of soft synths, but more importantly it's because projects with Guitar Rig loose their amp settings after a re-install and I haven't tracked down where it stores the data.
 
So where should I start?

Check this thread.
http://forum.cakewalk.com/m/tm.aspx?m=3140348

That was very helpful - thank you. 
 
It's been recording fine now for 9 minutes, so I'd say that's resolved. Interestingly I reduced Playback I/O size from 256 to 128... and enabled Read/Write caching. This seems to contrary to a lot of advice... but it worked!
 
My audio cache is on a non-boot but mechanical hard drive. 
 
I'm guessing a non-boot small SSD drive would improve performance and stability. I'm thinking of getting more SSD's once Christmas has been paid for!

Here's a bunch of useful info on optimization in SONAR. It's the link to which the "help" button in the drop-out dialog box directs you.

Tony,
I don't think that SSD drives are recommended for the "project" drive.
Project meaning where the .cwp file and associated audio are kept.
You are using "per project folders"?
Your description "My audio cache is on a non-boot but mechanical hard drive" is the "correct" way
to organize your DAW.
ie: D:(call it Audio)\projects\my song\audio
However, this should be a 7200rpm drive, preferably NOT a so-called "Green" drive.
SSD is great for all the samples associated with any VSTi's that you have installed.
 
Tom

Tony, I am glad it works now. Have fun!

Ta 
 
My audio projects are on a separate hard drive, it is indeed a 7,200rpm model and not a green one. It's my L: drive due to DVD and virtual DVD drives. 
 
I ran Performance Monitor on it and noticed that during recording it was writing to the same hard drive. It must be configurable by a folder location. SSD's have a finite number of writes, the trade-off for performance I guess. Having one for a project folder would be fast but risky because it's more likely to fail. But if during recording it writes to a temp location first... then I could see it helping. That's a big if which needs a little research though.
 
Later in the new year I think I'll get an SSD for my soft synths because that's read intensive.
 
Thanks again for the help.

If you specify a project name then Sonar writes new audio files to the Project folder directly.
Without a project name it uses the Global Audio Folder again directly.
 
In other words, my theory was wrong - there is no cache folder.
 
So an SSD for the project folder would be risky due to the number of writes.
 
I disproved my theory by using Task Manager -> Performance Monitor and then filtering the CPU by process Sonar.exe; you can see which folders it is writing to.