hpimidwest, it is possible that it is your bulb.It could mean that your lamp is old (4000-5000hrs) but it could also be your ballast. As the lamp gets older, it requires more voltage to spark or ignite. If you still have a picture, just dark/darker you are a bit in a catch 22 situation. You can buy a new bulb and hopefully that will resolve the issue, but if it does not, you would have to replace the ballast. You may end up purchasing both. There are numerous variation of ballast and bulbs. We'd need the exact model number to help you out further.