There is indeed a bug with one of the sight textures of the SCARs, at least that is what Scuba told me (he accidently added a bad format texture). There is a hotfix in the making, but since there isn't a hotfix installation thingy it can't be released yet...or something like that :O_o.
SO, yes there is a bug witch affects the SCARs only. NO, redownloading the full or patch won't fix it. So no need to punish the file providers by retrying to download it!
All i can say is it is getting looked into and a fix will be released asap.
In name of ACE, sorry for the inconvenience.
Additional info from the ACE forum
Issue confirment. Note that the incorrect texture format only effects ATI users.