Vim creating backups despite backup being disabled in rc

Hi,

I am using Vim version 7.4.430 on FreeBSD-10.1 (i386). The last line of .vimrc is :

set nobackup

Yet whenever I edit a file, Vim creates a backup file .<file>un~

I had never seen this behaviour in Vim, and it is getting annoying as it is messing up my filesystem. I tried inserting the following line to stop the behaviour :

set nowb

But that too is not working. Can someone please tell me how to force the original behaviour as in version 7.2 (where nobackup means exactly that) ? And, BTW, why was the behaviour changed at all ?

Thanks &  --   Regards,    Manish Jain  +91-98995-82709