I take it you are using Vista's own burning suite ?
You do have further options,try Imgburn to burn your discs click here or deepburner click here
If one or both work for you,we know its a windows problem.
Of course it could be the media,as RW's can be very finicky at times.
My advice to you would be trial and error and stick to a brand that works best for you.
I personally prefer Datawrite or Verbatim discs,and very rarely use RW's as these have proved to me in the past to be unreliable.