gear problems

I cant select gear when the engine is running, I can select gear when engine is off then start with clutch depressed but can only drive in the gear selected i cannot change gear, is this a clutch problem, transfer box problem or gearbox problem pleae any help would be much appreciated

Clutch.
Very unlikely to be Transfer box - in fact I have never known a T-Box to fail on a freelander.

Almost certainly a clutch problem. There is sufficient drag from the clutch when trying to change gear with the engine running to spin up the gearbox and prevent the syncro rings allowing engagement.

Pre-selecting the gear and then starting will force the driven plate to slip within the clutch housing.

Have a look at the slave cylinder and bracket first.
I have sorted 2 hippos with the same problem due to this nice and easy fix.
Its a crap design and it fatigue cracks next to the slave cylinder attachment allowing the bracket to flex too much not allowing the clutch plate to disengage fully. Eventually will snap altogether or break the slave cylinder.
Good luck

If its a td4 then the slave is a concentric in gearbox slave!!! So the only way to change is to remove the gearbox. So you might as well change the slave cylinder and the clutch at the same time.
I had mine done last Dec and it was about £470 for new clutch, new slave and fitting. I believe that was a very good price. It was too cold outside to do it myself