Well, this is simply a hard drive error. I got the same with raw/sounds/   folder, but I managed to get it back. Now, the corrupt folder is the one called Techniques, inside raw.

I was wondering if someone could upload that folder for me. Now I can't compile my map, also, i have to reconvert all my custom textures (nearly 50) thanks to trying to fix the error by running the converter again.

Anyway, thanks a lot for your help.