Are you an administrator? Vista doesn't think so...
"If you change the file properties from read-only to read/write (ie uncheck the read-only file attribute), it comes back as read-only!!! What? I uncheck the checkbox, close the folder properties dialog window, and re-open it only to find the read-only checkbox selected. And yes I’m in Admistrator mode."
My thoughts exactly...
http://www.followsteph.com/2007/06/17/windows-vista-read-only/