Hi there 
I m running X3 since a while and love the workflow and cleaness !
But already soon after starting using it (Win7  64bit), it caused some serious problems and crashed regularly.
And I mean really serious stuff, like:
suddenly out of nothing
- Soft Synths change their sounds
- all FX in the mixer are turned off
- it crashes very often when saving
 
This is very disappointing and frustrating!
 
Does anyone experience such issues too?
Greets
 

Sorry to hear. Are you running X3e?
Have you installed the 64 bit version of SONAR? Are you using both 32 bit and 64 bit plugins?
BTW, this forum is for 8.5 and older.

I recommend you do 3 things.
 
#1 De-frag your hard drive(s). Defrag the hard drive that saves the Wav files and then defrag the hard drive that has the cwp files that Sonar uses as the song file.
 
#2 Check your audio bit depth settings. You might have the settings set incorrectly. This can happen occasionally by some mysterious sequencer God. Yikes! I can't believe I said that! If the bit depth is set to 24 and you recorded in 16 bit the audio can really get messed up. Sometimes the VI are in 24 bit and you are recording in 32 or 16 bit. What I generally do is establish what I will use for all of my projects and then stick to that for the sake of not having problems you seem to be running into.
 
#3 I'd install a program called Malwarebyte (it's free & it's awsome) and scan your boot drive for a nasty. This is the best crap finder I have ever used and I run it once a week. I'm shocked with the files that even well respected websites leave behind to spy on your habits and these nasty's are executed every time you touch the keyboard or mouse. I can't get believe that this happens but it really throws the machine into a tail spin so, it might not solve your problem but it is something that needs a once a week habit. 
 
I use the 64bit Win 7 setup and have never had any issues with this setup but have had a similar problem using XP.  I hope some of this helps.

#1- Not necessary with windows 7. Old school thinking and not possibly linked to OP issue. 
#2-Just plain wrong and absolutely nothing to do with OP's issues. Sonar works in 32 bit floating point. 
#3- I'm sure the OP is aware of scary things on the internet. And besides a serious DAW or any important computer should not be on the internet, or at least only used professionally for needed updates. 3rd party software just ferrets out a lot of totally harmless files to justify it's existence. Use a respected anti virus. I know your trying to help and I usually ignore these things,but there was just too much wrong info in your post and some people might believe it. 
 
OP- you do not give us any information other than you are using x3. 
Are you using a audio interface, what are your computer specs
Have you installed all updates and drivers? 
And yes this is the wrong forum for the x series. 
Why don't you start a new thread there and post info about your set up to get an accurate appraisal of your issue. 
Even better add your system specs to your signature like most of us have,, see mine below. 
The more details the faster the issue will be solved. 

Uruxon
Hi there 
I m running X3 since a while and love the workflow and cleaness !
But already soon after starting using it (Win7  64bit), it caused some serious problems and crashed regularly.
And I mean really serious stuff, like:
suddenly out of nothing
- Soft Synths change their sounds
- all FX in the mixer are turned off
- it crashes very often when saving
 
This is very disappointing and frustrating!
 
Does anyone experience such issues too?
Greets
 

I am having the same problems.
 
I am trying to run Sonar X3D build 323 (x64), on windows 7 64 bit and it crashes on every project save.  Very bizarre.  Cannot get it to run cleanly.