file permissions

[twelve]

i cannot write or delete files to a couple of folders on my stora
this has only just started
it is only on two folders all sub folders and files in the two folders share the same problem
i have looked at the file permissions with filezilla and the file atributes say 770 looked at the other folders i use on the stora and they say 777
tried to change the folders to 777 with filezilla it would not change them
can any one give me some advice what to do next
Thanks
Mick