Ummmm... guess what happened to me this am? I need to post pics of this because nobody will believe me without them... After replacing my leaky clutch master cylinder yesterday and bleeding it... I drove home & everything was fine. But this morning while driving to work, my whole clutch pedal assembly broke in half. It's lying on my desk next to me. My car's at the shop thanks to a flatbed.

Needless to say, other things than hydraulic issues can cause the same problem you're having. I fired a spring out of the clutch disc that's in it now. It chattered for about 50 miles afterwards, but still works fine so I haven't bothered replacing it. The clutch linkage can wear out causing the tolerances for the throw on the master cylinder to be off, and just a fraction of an inch there can make a big difference on the clutch's operation.

Broken clutch forks can also cause this if only one side of it breaks. Seen that happen on a couple Galant VR-4's. Maybe I was wrong with the 90% chance estimate.