The hub just needs some service. It's easy to do yourself you just need a 10mm and a 5mm Hex wrench. It isn't even necessary to remove your cassette to open the hub. (but it makes it less messy. )
- Just pop out the plastic end-cap on the left side of the wheel (Where the QR goes through) and put in the 10mm hex wrench.
- Put the 5mm hex wrench in the right side axle and open while while holding the left side.
- Take out the right side axle and carefully slide off the freehub.
- Make sure you do it slowly and above a table or something because the two pawls might want to jump out.
- take out the pawls or let them sit. (You can get replacements from your lbs that sells mavic.)
- Pull out the left side axle from the left side.
- Clean and lube everything. Check if the bearings are all still smooth. (there are 3 of them! there is 1 in the freehub and 2 in the hub)
- Put everything back together in reverse order with some thin lube.

Once you learn how to do this it becomes a 5minute job. I do this once or twice a month on my wheels. Keeps them from wearing out and problem free.

Greets!