Viewsonic PJ551D projector suggested lamp (bulb) replacement. Put in brand new bulb, getting same error msg?!?

I've been getting the "you should replace the bulb now" warning for almost a year now, but there has been no degradation in the quality. Still, I put in a brand new bulb, and after turning it on twice, I get the same warning every time. Anyone have any experience with this? Could anything else be causing this warning? Again, it's worked great all along except for the warning.