I think my light meter isn't working right. Has anyone had this problem? I always shoot manual and use the light meter as a guide to expose the shot correctly. Recently it seems to be off a bit and shots are over exposed. Is there something I can do to calibrate it...?

Jen, is this a portable light meter you're talking about here, or the built in one in the camera? If it's the portable kind, are the batteries fully charged? Just throwin' an idea out there. I haven't used a light meter in over 30 years, so forgot most of what I know about light meters.

I bet that is really irksome...I left my handheld meter at home on Thanksgiving and all of my shots are underexposed. Does the D90 have an exposure compensation device or menu selection? Maybe you have somehow changed the parameters exposure compensation wise??? Just a wild guess...

The same thing happened to me one afternoon. Lucky it was nothing but fun shooting. Nothing important. What I found was I had left it set on +2 for only the Program setting. If I am not mistaken you can set each mode separately. I sit down at home at least once a week and go through each setting and make sure they are each set correctly for starting.

Also iPhone has a Light Meter App that is pretty good.

Its the built in light meter. I figured it out... Thanks to eye level I checked my exposure compensation and somehow it was +2.7. I didn't think to check because I always leave it at 0. I don't know how it got changed but, man am I relieved.