SSAS STDDEV function leads to wrong results

Earlier last spring, I created a cube containing some calculated measures that were using STDDEV function. Everything seemed to be fine except when STDDEV was used over similar number series. I sent post on SSAS MSDN forum and did not get any viable solution. Here is the link to my post:

http://social.msdn.microsoft.com/Forums/en-US/sqlanalysisservices/thread/e0d7651e-a874-481c-a07c-0cde939ad327

Is the STDDEV built-in function buggy?