Sonar crashes even after opening in Sonar safe mode removing all plug-ins at same point.

Doing post work on  a set of multitrack video/audio recordings. When I move to a certain part of the timeline towards the end, hit play, and Sonar says bye bye and it won't open again without rebooting the computer. (I have gone deeper into task manager and ended the program and that seemed to work but not the standard place in task manager where you end program. Normally I would just start a new file and copy everything and I will do that now as it seems I have no choice (extensive time sucking) but wondered what else it can be.
 
PS What I am doing in the meantime is open up my backup which doesn't have my tweaks/plugs/etc. and just working on the songs that I couldn't process (only two left.) This seems to be working, but of course an inconvenience for the video person as i can't do one long render for timings sake. C'est la vie.

I too have an 1818VSL and it works fine in Windows 10, using the current driver from their site.  Michael also has Windows 8.1 listed in his signature, and the interface worked fine in Win 8.1 for me.
 
I would suspect some plugin loaded in the project is having a bad hair day, or possibly some project file corruption.  
 
You can try loading the project in Sonar's Safe Mode - skipping any plugin load - and then try moving around in the project to see if it works (don't save it that way, it is just to test out the removal of plugins on the issue of crashing).
 
The other suggestion I have is for you to create a new project folder, named something similar to your project, then create a sub-folder called Audio, then open the project normally, and then do a Save As, to that new project folder you created - checking the box to copy all audio to the new project's folder, naming the project file the same as its folder's name, for consistency.  That might correct some kinds of data corruption from the original project file.
 
Bob Bone
 

could it be related to the video format? there are some video users around the forum who might know, maybe add "video" in the subject to get their attention