I'll be interested in hearing what you find out at the vet's office. Our first cavalier, Gizmo, had very similar behavior to what you described in the first part of your message. He ended up being diagnosed with flycatchers. This was about 9 years ago and he was just a little over one when he started having problems. At the time many people believed that this was a seizure disorder. I think now that opinions are a little more divided as to whether it is a seizure disorder or some form of obsessive disorder.
Many times we didn't see the original "seizure" (the frantic runninig around and acting as if he was trying to catch flies) but we did see the aftermath. What happened after the seizure is that he would hide in corners and act very frightened. He seemed very upset.
He went on potassium bromide after seeing a veterinary neurologist. He was on it for the rest of his life. After starting medicine he had only a few few "breakthrough" seizures.
Hope you get good news.
Margaret, Newton, MA - Gadget (blenheim), Sasha (ruby), Wyatt (blenheim)