Win7 x64 backupcopy=yes

[nowhereman]

I'm experimenting backupcopy=yes on Windows (7 x64); now when I
overwrite my _gvimrc I get a

E212: Can't open file for writing

I know I am supposed to keep backupcopy=auto, but I saw I get the same
error if I disable the backups altogether with

set nobackup nowritebackup

I was wondering why.

( more info: http://www.reddit.com/r/vim/comments/fq9cd/backupcopyyes_and_windows/
)

thanks in advance.