Cryptanalysis of the Random Number Generator of the Windows Operating System. Leo Dorrendorf, Zvi Gutterman, Benny Pinkas.
Dorrendorf, Gutterman and Pinkas have reverse engineered the random number generator code from Windows. According to their paper, it is easy (O(1)) to compute a previous random number and possible (O(2^23) to predict the next one. (via The Inquirer)