Hi guys, ive been watching this thread some time, finally have something to contribute.
When using DDSopt ( pre-release 3-5755-0-8-0-upd3) on the vanilla textures from textures.bsa, ive noticed several corruptions after optimization.
effect\cloudtilefrostsmall.dds
effect\fxcloudroundtile.dds
effect\fxcloudroundtilelite.dds
effect\fxcloudroundtilestrip.dds
Also every file in the sky\ directory containing the word "cloud". 13 files in total + skyrimcloudsfill.dds which has already been mentioned as turning the horizon purple.
When processing the same files with DDSopt pre 5b there is no corruption (except skyrimcloudsfill.dds).