First, are you sure it's only MayaStudio's stuff? Your download program may be having issues. Second, you probably need to run them through the MAC converter as the files are PC packaged. MACs need a little help to be able to read them. There's a free stuff converter here which will allow you to use most Poser PC files (such as textures) for MAC computers. Are you using P5? Some of the textures get a bit whacked in P5 - it's not the texture makers' fault. This has happened with a good number of excellent textures from various people. Try applying a displacement map of .000003 or so to fix it.