if a baker could enlighten us as to the other program then it should be easier to troubleshoot

"This action cannot be completed because the other program is busy." 
 
Check to see if your project hard drive is set to spin down in power settings. That's the only time I get that message. Wait a couple seconds for the drive to spin back up and hit retry.
 
Steve

No, drives are set to never power down.  This only appeared for me after X3.

Could it ne that you've.had another program open that was using an audio device that Sonar is expecting to be available on opening?

I wish I knew.  The only other change to my system was installing Jingo on the advice of Dan Gonzalez, so I could post a video of the weird vst GUI issue.
 
I'm wondering if that could have something to do with it, as it now seems permanently on, unless I manually switch it off.
 
As for the other issues, it would appear that I am the only one, which is strange, because CWBRN-20548 is marked as repeatable, and now submitted to developers.
 
Thanks everyone for your thoughts on the "busy program" message.

Last night I got the pop up message when I when I completed working in one project, then opened a new existing project. Makes we wonder if there is a lag in Sonar releasing the interface driver, or perhaps something in the background...
 
Next time I see it I'll try waiting a few seconds before clicking retry

Thanks Sixfinger. I get it only occasionally, even on first opening Sonar, but I wonder if it has something to do with Jinga in my case.
 
I'm also interested to see if anyone has seen this behaviour from X3:-
 
Last few of days I have had some oddities:-  

• Following a crash, I opened up a Project (started in X3) and the counter in the Transport Module was completely blank, even as project played.  When I switched screensets, the light blue luminous box the counter is in seemed to stay in the same place, regardless of position on Transport Module.  Closing Sonar and Restarting computer returned it to normal.
• Just now I was creating some track templates in a blank project (started by ctrl+n) to save.  I created a Guitar template, with PC modules - 4K Expander/Gate,  76 compressor, Quad Curve EQ, Guitar Rig 5 (in FX Chain), Tape Emulator and Console Emulator.  Having saved the template, Sonar hung, and then crashed, sending a problem report, marked as reproducible (CWBRN-20548) (and now submitted to devs).
• Strange disappearing Plug GUI's when switching screensets, which Cake reproduced when I sent them a project.
• I'm still noticing occasional redraw issues with the PC Ca2a module, where the title bar appears twice, but returns to normal when moved.