Sounds to me like the second fob is goosed if it no longer starts the car (transponder code wiped)
Does the other one start the car? I sure hope so for your sake.
If not, you may be in a pretty poor position and will need to contact Renault dealer to see if a new key can be ordered (should be OK but will cost you a few bob indeedy)
The other may resynch for unlocking the doors (if that's it's only problem), search the forum using the search feature for the correct procedure for your car, do both plips at once, the second will more than likely not work but the first may start working again as it may only need resynched to open the doors provided it starts the car.
Renault recommend using keyfobs in an alternating fashion, week about, as the unused one will eventually go out of synch as most remote keyfobs use a rolling code system, beyond a point the code will be too far out of synch if the keyfob has been sitting in a drawer too long and will no longer operate the locking. A non-starting situation cannot be caused by loss of synch, only central locking operation is affected by this.
Everything I have said is assuming you have remote central locking from a button on the keyfob.
hope this helps/clarifies things for you.