Steven, in addition to what Flying_Meat said, can you list a couple of the affected files - their names (including extensions, such as .txt) and their permissions (if you're able to see that in OS X - i don't use it personally)?

Because I'm curious what you mean by text files being converted into executables... I don't think I understand entirely what you mean. How do you know they were "converted to executables" and were not simply corrupted somehow?