Grinding Sound When Engaging Clutch

I was driving my car (340/833) home recently and all seemed fine until I got about half way home. I pushed the clutch pedal in to downshift and when I let the pedal up there was suddenly a short grinding sound while the pedal was coming up. Once the pedal was all the way up and the trans. was in gear it was fine but each time I depress the clutch pedal it makes this sound when I let the pedal up. I don't hear any noise when pushing the pedal down or while in gear and the car is moving, only when I depress the clutch pedal and let it back up again. I'm suspecting the throwout bearing at this point but I am not sure. I don't know how many miles are on the clutch and related parts but I have owned the car for 14 years and put maybe 1500 miles on it during that time. I am going to try and get out in the garage soon and look into this but was wondering if anyone might have any thoughts on what likely the problem is.