From: Moire Georgette
it happened with my alt yesterday, i tried changing clothes, changing skins, even cleaning the cache didn't solve it. what *did* work for me, for some reason, was copying the skin and wearing the copy. worth a try.
I don't know either, but it seems like skins can occasionally become corrupted, while a copy will work fine (presumably because it creates a new asset).
[Ctrl-Alt-D or Ctrl-Alt-Shift-D to bring up the debug menus]
[Client / Character / Rebake Textures to rebake]
[Edit / Preferences, Network / Clear Cache to clear the cache]
* Right-click on yourself, Take Off and remove all clothing (you'll want to be somewhere private and non-PG

)
* Try a rebake first of all, going into Appearance may help nudge it
* Failing that, make a copy of the skin (Click it and Ctrl-C), then paste it into another folder (Ctrl-V) so you can keep track of what's the copy and what's the original
* Change into a different skin altogether (use one of the default ones in the Library)
* Clear cache & relog
* Rebake
* Change into the *copy* of the skin
* Clear cache & relog
* Rebake
That usually seems to fix the problem for almost everyone

. If it still doesn't help, and you couldn't see the clothes when you changed into a different skin, you may want to contact the skin creator and ask for a replacement copy.