I bought my car with an aftermarket clutch and master cylinder, and ever since I've had it the clutch pedal squeaks like crazy. In general, my clutch has a pretty harsh engagement (lots of chatter), but I've noticed every now and then there will be a day when the pedal doesn't squeak, and the clutch engagement is also much smoother on these days. Does anyone have a possible explanation for this?

edit: I've tried spraying lithium grease on the pedal/mc assembly, seems to have no effect.