I had similar problems 3 weeks ago, I would have to agree on the thorowout bearing. After replacing it no more problems.
Was the car shaking?Also the engagement was different, the clutch had a different feel and it popped back differently.
Also I was having grinding in reverse. I was bleeding the clutch during the problem period, felt fine afterwards but the problems quickly returned. If it grinds, put the car in gear while it is off then start it.