What I would do, and remember I'm a dum dum, is go into the Sonar VST scanner's file paths to see if anything in there is pointing to your s drive.... AND I would go into the s drive itself to look for any plugin/Cakewalk/whatever files that should not be there.
Sonar is reaching out to the server drive for a reason. It thinks something it needs is there. Disconnecting it probably just removed the path from the scan automatically and once you hook it back up again it'll start hunting again.
Again I say... irdum... just making suggestions of where I would look first.
Edit: and of course if you do find any paths or files that should not be make them not be anymore (delete them).