Milan: I tried the test in comment #11 and had no unusual output. The password changed successfully in the second terminal.
Using the GUI, it hangs every time and does not change my password. I tried this from a fresh install first, and the problem continued after several after running all updates on Feb 26, 2011.
UPDATE: After successfully changing my password from the terminal, the GUI utility works fine for subsequent changes. In case any of this info helps: When I had the problem, it was the first time trying to change my password since the install, and I did fail the first attempt because I was just changing the case. I have my system set to auto login.