Sorry to dig up an old thread but this is happening to me right now. And it's got me stumped.
I bought my r34 gtt end of last year and only have opened the car using the central locking.
I had a flat battery in the car after leaving it over the Xmas and new yrs holidays. The car wouldn't unlock using central locking. So automatically I went to try open the car door using the key, and both doors won't unlock using the key. Tried the boot and it opened fine. So I called the previous owner and asked if he had problems unlocking the doors with the key, in which he replied he's had flat battery before and the door unlocked fine with the key...
Anyway, I ended up unlatching the hood and put jumper leads on the battery to another car to unlock the gtt with central locking remote.
But the key still won't turn on both doors...
Any ideas?
(I don't have a spare key)