I didn't use Sonar Platinum in a while. Last time, shortly after Cakewalk spectacular collapse, it seemed to be pretty stable on my system. Today, it didn't load anymore (Windows 10 Pro 1803 last updated in August 2018). Instead, a Windows Installer little window opens and I am told that the computer is "Preparing to install". Preparing to install what? i don't have any idea. And, of course, nothing happens further; i have to open the task manager and kill Sonar. In the years I was always criticized for talking badly about Cakewalk and their support I would've expect to hear that "it's a Windows problem, no doubt about it". But all my other programs are working fine, except for Sonar, a program I paid for to be updated 'for life". The life of a butterfly that is, but nobody mentioned that at the time. So, if there is anyone left on this forum who had the same experience, please, let me know if there is any fix out there or the butterfly is dead and our money gone for good and for nothing.

Uninstall, than reinstall SONAR fresh. Problem solved easily.
 
 I would also HIGHLY recommend Joining Bandlab and getting the fully updated version a.k.a Cakewalk by Bandlab right after reinstalling SONAR. 

Although the OP did not provide information about the audio interface chances are it is from a Yamaha company. This is a known problem with their audio drivers. Remove the driver if no longer using the interface or reinstall it. Either action should solve the problem.

You were right as always, scook. It was a Yamaha driver used to connect a Montage 8 to Cubase. I uninstalled and then reinstalled it and the problem was solved. Thank you very much.

For what it's worth, although Sonar (and the company who supported it) is no more, the program based on it and exactly compatible, Cakewalk, is still in development and has new releases about every month.
 
You can download and install it for no charge, run it alongside Sonar, and all the extra plug-ins you got with Sonar will work with it plus it has several new features of its own and is way more stable.
 
So you might say the butterfly just went into a cocoon for 5 months and emerged looking different, even prettier. Give it a try! Everything works mostly the same, only more convenient and not as crash-y.