I'm sorry, I should have posted about this earlier. Make sure the tool (or geoprocessing settings) is using nearest neighbor.
And, more importantly, the cell size is 30m. The difference between WGS84 and NAD83 in the contiguous US (48 states) is about a meter. I wouldn't bother reprojecting the raster. Use its property page in ArcCatalog or the Define Projection tool to set it to NAD83.
Melita