problem with my roof
 

the convertible roof of my boxster no longer opens. It seems that it is blocked. Is it a common problem or it is motorisation of the roof?

Try the easy things first. Make sure the latch is completely unlatched and the hand brake is on and the brake light shows on the dash. Then check the fuses.

Before you snap the cables or arms you can open up your factory owner's manual and follow the procedure for opening it manually. I can give you the shortened version, pop off the 2 shocks in the mechanism (need nothing more than a screwdriver) and you can lower and open the top manually and see if there is any binding before you break something. This will allow you to watch and feel the mechanisms moving and you can spot a a problem and remedy it before breaking something that will be more involved to repair. If it's not moving freely, don't force it. One of the arms could be out of adjustment or something is binding, I have experienced some binding on the lower slides so a little cleaning and lithium grease was necessary.