I have recently setup a new Exchange 2010 server.
When I log into OWA and then click on 'Options' - 'See All Options' I get redirected to a login page displaying the following error, "The user name or password you entered isn't correct. Try entering it again.". Subsequent login attempts with the same user result in the same error. This is related to ECP and not specifically OWA.
I've tried running the following commands from EMS:
get-ecpvirtualdirectory | remove-ecpvirtualdirectory
and then restarting IIS. This didn't resolve the issue.