I fixed mine yesterday, had what sounds like the same problem as you. The door was shut but could not open it as the door handles moved but did not operate the latches.
I had little idea what I was doing, but
1 Remove the door handles ( two screws on the inside ) and pull the handles and square bar out.
2 Look through the hole. On mine the square hole the handle square bar fits into had broken up so the handles could move without operating the rest of the mechanism.
3 Spent half an hour trying to open the door by putting the square bar into what was left of the square hole, wedging a screwdriver into the remaining gap and turning the handle. Failed, but worth trying.
4 Took the door centre panel out. Remove the black rubberery plastic strip ( called the gasket?? ) from one side of door. Then remove the plastic strip from the other side.
5 Lift out the centre panel
6 Now the fairly brutal, totally unscientific bit. Large screwdriver between the door and frame in the viniity of the top latches, lever the door away from the frame enough to see the latches in the ( very small ) gap. Without the centre panel the outer section of the door gives enough. Fiddled around for a bit until the latches came out.
7 Removed the whole locking mechanism, replaced just the lock section ( about £30 from good old E Bay )
8 Replacement is reverse of above, without the levering bit.
9 Lining up the door took a few attempts, the centre panel is braced in place with an assortment of wedges, you have to set these so the whole door is locked rigid and latches aligned with their gaps in the frame.
10 The levering out of the latches took more force than I ecpected, bent my 10 inch screwdriver doing it.
Hope this helps somenoe
Best of luck
Keith
Keith, April 2011