I had the same error in the FPS tutorial with lerpz (page 19 I think) and I fixed by selecting the "Near Camera" in the hierarchy window and in the Inspector window changing the tag to "Main Camera" in the drop down list. I was also getting several
NullReferenceException
at (wrapper managed-to-native) UnityEngine.Component:get_transform ()
at FuelCellGlowLookAt.Update () [0x00000] in C:\Documents and Settings\Owner\My Documents\3DPlatformTutorialStart\Assets\Scripts\Misc\FuelCellGlowLookAt.js:7