Read an article that blamed Flavio Briatore for the problem, his decision that his team (now Lotus) would develop KERS and not Renault may have led to these issues. The bad boy of F1 strikes again.
http://www.autosport.com/news/report.php/id/112596
Williams has had one of the most reliable cars in testing with a Renault powerplant, so someone is doing something wrong.