You most likely have corrupted game data. Get a md5 filechecker (for example this one) and verify your files. I can't guarantee my files are 100% undamaged, but I didn't have any glitches so far.

Here is the list of checksums from my client: http://www.mediafire.com/?u6a6db0mtrn68pc

If the files come up as OK then you have some sort of hardware damage. Either you GPU (most likely) or RAM

OR, FFXIV is mutating into The World.