I have the exact same problem! Strange I come on here to complain and see this thread haha! If I put it in 1st then go into reverse it's fine which makes me worry it's the synchros.
I really can't afford to get a new gearbox and I've just had the same problems with my last car (350z), although that was with 6th and crunched when I tried to put it into gear, whereas this case seems to be different as it just doesn't go in.
It's just recently had the linkage bushes replaced too?