ive only seen this due to a plug in manager path that was entered incorrectly or a vst folder deleted or moved completely.
it could possibly be a update or reg thing but try to put that folder back you said you had moved and see what happens.
its possible this folder contained sensitive material need to operate sonar correctly.
but hey... right now anything is basically a guess until we see something positive :)
i'll keep poping in to see how your making out.
PS- sometimes task manager can prove effective in seeing something else like a possible virus.
I know you probably don't have a virus but sometimes thumbing through task manager one can see something that just does not look right.
like jbridge / bitbridge not running.
or even something running that would prevent sonar from opening up properly.
for instance if sonarpdr is running its impossible for sonar to exe at all.
unlikely in your case because you at least are able to open up the main program.