I had the same issue.
What it turned out to be was the fan not running due to ice buildup around the fan enclosure.
The Fan is accessible from inside the fridge. Simply remove all shelving and you'll see a panel at the back lower part of the fridge compartment. The front cover of the panel probably says Twin Cooler on it..you'll have to remove the zigzag pipe in front of it to remove the panel too.
But anyway, remove the panel and you will see the fan mounted on the reverse with the impeller sat inside the insulation panel. Simply remove the four mounting screws to remove the fan and use something like a hairdryer to defrost and remove the ice. Also there should be a water run off at the bottom of the fan which I had to make a little bigger as this was blocked too. It's polystyrene and so a sharp knife did the trick.
20 mins later having defrosted the ice around the fan completely I then re-assembled and bingo! fridge would then cool.
before I put the fan back together I held the door switch closed to infer the door was shut and I watched the fan start up. THis made sure the fan had not burnt out. I then completed the box up and the rest is history.
Hope this helps.
If you want a picture let me know and I'll post one.
Becks.
June 2010