We have the same problem. I use a small electrical screwdriver to gain purchase on the side of the plastic catch which I can then gentle rock back into the open position. It's quite easy when you get the hang of it!
You can also take the front panel off and do it that way (which I used to do)
Ours is worn so I'm looking for a replacement catch - but yours may be o.k. if it's a one - off.
Hope this helps
Mark
October 2007