I had the same problem and someone told me the solution. Take the lamp cover off and inside you will see a brown block that pivots right in the corner of the lamp holder, try moving it forward with a screwdriver and if it comes back very very slowly then use a cotton bud/tip spray some silicon spray or WD40 on the bud and dab the grease on the left and right side of the pivot (one end has a finishing cap on and the other side is covered with a small spring. It's easier to remove the bulb.
This block is something to do with the lower iris as I was told, seems to be a very common problem with them!
Once the grease has been applied, use a small screwdriver to move the block in it's full range and eventually it will spring back in under a second.
www.youtube.com/watch?v=6jGwB05_gdk
Iain, December 2009
