Maybe a bulb going bad?
Without doing some tests this is difficult to know.
I do not remember if the bulb in this model is a gas discharge type or a filament type. I will first indicate here for the filament type.
Make sure that the unit is switched off, and is unpluged from the AC mains.
With a DVM it is possible to check the socket contacts. The unit would have to be unassembled to gain access to the lead wires that go to the socket, and the socket disconnected. With the lamp installed, use the ohms scale to see if the resistance of the bulb's filament can be measured.
If the socket contacts are okay, it is possible that the fault is the power supply to the bulb, or it can that there is a cooling fault, or maybe the bulb itself has an intermittant where when it gets heated up it temporarily becomes open circuit.
The way that most electronic equipment is designed today, it is microprocessor controled. There are sensors for temperature, current draw, quality of voltage regulation, air flow for cooling, specific performance checks, and other similiar things. If there is an error, the uPC will shut the unit down. In most cases, an error code of sorts is indicated. In some equipment, there is no displayed error code.
For the gas discharge type of bulb, to test the socket contacts to the bulb, instead of measuring the heater resistance, you will need a dummy insert to replace the bulb that has a zero resistance for testing the socket. You insert the dummy tester, and measure of the leads with the DVM to indicate if the contacts are okay to the bulb.
A less sure way to test the socket contacts is to disconnect the socket from the supply, and measure the resistance of each lead to its respective contact in the socket. This will indicate if there is open or closed resistance to the socket contacts, but does not respect the tollerance for the contacts to make a connection to the bulb contacts on its base.
In the service shop, after all the above has been done, the tech would do his tests by trying modules and parts until the fault is located. That is if the fault was not the socket.
on Apr 28, 2008