Dark Screen

The lamps in these normally last about 3000 hours (if your really lucky). The bulb will start to loose it brightness as a matter of due course at about the halfway mark. It maybe that you are running the unit in the non economy mode that they are fading faster then normal.
The sets have a reputation for not being good with lamps though.

Have a look at the lamp though, make sure it has been off for at least an hour to let it properly cool and check for dust that has settled on it. Also if you wipe the lamp, make sure it is with a dry cloth, or allow plenty of time for any moisture to completly dry before turning it on if you use a damp cloth.