I inadvertently used Ozone 5, DirectX, instead of VST on a song mixdown.  I had never tried it before so I don't know if it ever worked, but using Ozone 5 and DirectX caused X3b to start acting flakey (no keyboard control) and loss of audio.  Selecting one of Ozone's default presets it seems to be OK, but if I try a different preset then that is when things go bad.  The only way out of it is to reload the project and start over.  The VST version does not have this problem and what I've been using for over a year. 
 
I don't know if this is an Ozone 5 problem or an X3b problem, or an "operator" problem.  

I loaded the Cake TTS-1 directX soft synth and it has problems.  If you mute one track it mutes the whole synth, it causes crashes and audio drop outs.  I think it's best to avoid DirectX plugins in X3  

Jimbo88, since you also had problems with DirectX, I'll assume that its Sonar and not the plug-ins.
I wonder if the "c" update that is in the works addresses this?

I do not have Ozone 5, but took a look quick at the product specs quick. DirectX is definitely not preferred for plug-ins.
 
A couple quick questions come to mind.
1) Do you have all of the patches to Ozone 5 and *can* you insert it as a VST?
2) Are you doing this mix down with Win7 or Win8.1? The reason I ask is I have seen many posts on 8.1 drivers "not supported" or flaky. I have not upgraded passed Win7 yet.
 
From my lessons learned, I always bounce tracks to others prior to final mix down. This converts them to "audio" files but will leave the working tracks in tact in case you want to edit them again later. For the final mix down, I solo the bounced tracks, and then SONAR only needs to play with audio files and not the plug-ins for that final mix (this will distress the audio engine a lot). I have gotten burned enough that I always bounce tracks out of habit.
 
Something to try... if you bounce the track with Ozone 5 in it, does the bounced track sound okay for you?
 
Michael

An update and to answer your questions.
 
As I noted on my original post it works with VST and what I normally use.  I just accidentally selected the DirectX and had the problem - and the Ozone 5 problem only happens if I try a different pre-set, other than the first one I select.  Ozone 5/DirectX works OK if no second pre-set is tried.
 
This is on Windows 7, 64 bit.  I haven't tried it with Windows 8.1 as I only have Ozone 5 installed on my Win 7 system.
 
A new twist.  I added Sonitus Reverb to a track, and that is only available as Direct X in X3b, and it works without problems.  So its not that "All DirectX" is the problem.
 
Its back to the "drawing board".  Still don't know if its a Sonar X3 or Ozone 5 problem, but as Jimbo88 had the same problem with a different DirectX device it sounds more like a Sonar problem.
 
 
 

New Update.  I thought Sonitus worked OK in X3b but as it turns out it has the same problem as Ozone 5.  Also, I've had the same problem with Ozone 5 loaded as VST2 and not the original problem of Direct X only.  Thus, I have to think its a Sonar problem and not the plug-ins. 
 
UPDATE:  I have opened problem report with Sonar on this issue.  CWBRN-20980
 

Just install the VST version and use that.

I thought I made it clear that it has happened on both the Direct X and VST version of Ozone 5 with X3.  It did not happen in X2.  Sonitus, in X3, is only available as DirectX; it has the problem too, at least with the Sonitus Reverb. 
 
Finger pointing time at Cakewalk.  I opened the problem as noted above, Cakewalk closed it and told me to open a problem with Tech Support. I have opened a problem with Tech Support and waiting for their response. 
 
A workaround is to stop the playback and change to a different preset and then start the playback again. 

Sorry. Very late here. I misunderstood and didn't realise about you having VST installed as well.

Is the version of Ozone 5 you have 32 bit? If so you cant use 32 bit dx with 64 bit Sonar. I am a longtime user of Sonar and had Izotope Trash 1 that I used back in 2003. I bumped my Sonar 5 up to X3 and went to Win8 64 bit. Was disappointed to learn that I can't use 32 bit directx on 64 bit version. Could always install 32 bit Sonar and use it if I miss Trash enough...