My HP Pavilion dv-series notebook will not accept the user account password for the logged in user when resuming from sleep - message returned is Incorrect Password.

Simply selecting the Switch User option reloads the login screen and allows me to log in as the same user with the same password that was originally rejected. And, yes I've tried it more than one (hundred) times in case you were thinking it's just a case of slippery fingers.

Another interesting point is that it appears to be independent of the software running on the machine. Since the issue first appeared, I have done two clean installs where all HD partitions were wiped and new ones created during fresh installation of the OS. The first such clean install was of Ubuntu (Lucid) 10.04 amd-64, the second of Win 7 Pro 64 (from boxed disc and activated post install). Exactly the same symptoms, described above, are exhibited on both platforms.

Have engaged in significant amount of Googling an come up empty so any ideas are welcome.