Shortest code for Seven-Eleven

Ruby, 105 characters

Unfortunately I didn't get it below the 100 mark. It just brute forces all possible tuples and checks afterwards. Nevertheless it still finishes in finite time.

(1..m=711).map{|a|(a..m).map{|b|(b..m).map{|c|d=m-a-b-c;p [a/u=1e2,b/u,c/u,d/u]if d>=c&&a*b*c*d==m*1e6}}}

The formatted version looks like this:

(1..m=711).map{ |a|
  (a..m).map{ |b|
    (b..m).map{ |c|
      d=m-a-b-c
      p [a/u=1e2,b/u,c/u,d/u] if d>=c && a*b*c*d==m*1e6
    }
  }
}

Haskell - 121

(extra newline added for readability)

h=711
main=mapM(print.map((/100).realToFrac))
     [[a,b,c,d]|a<-[1..h],b<-[a..h],c<-[b..h],let d=h-a-b-c,c<=d,a*b*c*d==h*10^6]

This meets the requirements by only working with numbers with two decimal digits. It computes the solution (there's only one of them) using integer arithmetic, scaled up by 100. Floating-point arithmetic is too untrustworthy for this.