It seems to be grinding more and more often when I quickly shift from 1st into 2nd. It's a long, embarrasing, grind like I missed the shift or something, but it still goes into 2nd. Any ideas what this is?

I'm thinking it's clutch related, but I'd like a 2nd opinion. My clutch has almost 80k miles on it and the master cyl has a slight leak (but the fluid level is normal).