The stuff on the cheek looks like a problem with the geometry, like perhaps the vertices aren't welded where they should be. With a high resolution render problems like that will be exposed. It doesn't show on the low resolution because your sampling isn't high enough to expose those tiny flaws. The hair thing looks almost light a GI artifact, perhaps kicking up the quality, turning of interpolation, or kicking up the # of photons on the larger renders would help fix that. Nice textures BTW. Good luck, Eric Winemiller Digital Carvers Guild 3D plug-ins for Carrara http://digitalcarversguild.com

Eric Winemiller
Digital Carvers Guild
Carrara and LightWave plug-ins