I have Fulcrum Racing 7 wheels. Cycling in this morning I noticed what at first seemed like a slipping chain. I was surprised as the chian and cassette are in good nick. I then noticed that occasionally when I have been freewheeling and I restart pedaling that the freewheel would not engage straight away. This doesn't happen always, just occasionally. On wheeling the bike into my office, I've also noticed that my normal noisy bike is quieter, i.e. the normal clicking is absent (again, not all the time but every so often). What sort of problem does this suggest? Is this a common problem with these wheels? Am I looking at a bit of maintenance or a new freewheel hub?