[Hal Copple]

if it is an abrupt change, i would hazard a guess that one of the springs in your clutch disk has failed, and now prevents the clutch from fully disengaging

You might try to bleed your system, and put in a new slave cylinder, first, though. I had a slave cylinder go out at VIR, my car would not fully disengage. Let us know what happened, and good luck.