This is one of those "might help someone" posts. I often assemble drum parts by dragging in one-shots from the browser, which can lead to a lot of tiny clips. I was dragging and copying lots of these clips to create a second verse, and accidentally let the mouse button up before the clips reached their destination. This ended up creating a whole bunch of crossfades on the tracks where the clips ended up.
 
Sonar went into the "infinite blue circle chasing its tail" mode, the screen turned white, and I got the "not responding" error message. I've had this happen a few times before and at this point I usually wait a bit, assume I need to reboot, and reboot.
 
But this time, I was really hungry so I just let it sit there while I went to get a snack. When I came back, Sonar was back to normal. To play it safe I saved, closed the project, and re-opened; everything was fine. I deleted the one-shots that ended up in the wrong location and was back to where I was originally. I don't know how long it took to return to normal, but I was away from the computer for about 15 minutes.
 
Normally I wouldn't mention something that just happened once, but about a year ago I had the same problem (can't recall what caused it) and again, waiting for several minutes made things right. I thought it was a freak occurrence but now that it's happened twice, I thought it might help someone save their work when the thought they were about to lose it....

+1 I will typically wait, but it is not often very long. X3 is a challenging program to crash.

Thanks Craig. Great tip! I've never waited more than a short time when that happens. I just have figured it was a mess and went through the long route of either quitting out or rebooting altogether. I'll give that a try when I'm not in a hurry.

I would have hit CTRL+z before after I saved it and before I restarted Sonar. I've had the white screen happen, waited, and it went normal as well.

Leave it and wait is sometimes the best option. A few times I've tried to open an old project in Sonar and nothing happens for while, so I open Task Manager and see Sonar is "Not responding". Rather than abort it, I just leave it and sometimes it eventually comes good and starts working again.
 

I can also confirm that. I had an old X2 project with about 2GB of audio and about 30 Plug-Ins and it took at least 90 minutes to open it. There were no errors with the project. Saving it with X3, the next time it opens as fast as other X3 projects. So as long as you got the “Wait for the program to respond” message there is hope that your work isn’t lost.

I remember waiting a week once and true it did finally respond. 

I've done this quite a few times with the X series. I figure what the heck, wait on a restart or wait now. I find if I wait it causes less problems.

John, a week? Com'on!! :-)

John
I remember waiting a week once and true it did finally respond. 

wow...that would rack up some client hours now, wouldn't it?  :-D

I hope I don't need to put a smiley face on that post. LOL