If you've not tried it yet, what happens if you disconnect audio interface and all MIDI Hardware and reboot, then load Sonar, point it at the on-board audio (if it exists) and create a fresh project using the stock "normal" template (or a project with just MIDI tracks pointed at nothing if there's no on-board audio) and play that?
That way if the problem recurs the source would seem to be something internal to Windows, a driver, the PC or Sonar.
Another thing that might be worth trying is to rename Sonar's aud.ini file to something like aud.old so Sonar creates a new one.
A final thought that occurs to me is it might be to do with the mouse driver or associated mouse preferences software. I'm wondering if the mouse is getting continually polled by its software to check if it's doing anything and after enough time a lack of response does something strange, like a huge PCI bus latency spike or there's a memory leak. The problem not occuring earlier than 4 minutes because every time the mouse is moved or clicked whatever's doing the polling resets itself in some way. Years ago I had strange freezes that took ages to track down by the "switch something off and see what happens" method. The culprit turned out to be a mouse driver with a memory leak that polled non-stop and gradually used up huge amounts of RAM.