so someone else is having this problem too.
my blog is hosted on dreamhost, and I actually got this problem before upgrading to the latest version. i upgraded, and it persists.
I am getting the same symptoms as you are: I put in my account name and password, and the page simply refreshes back to the login screen. Same with “recover password” page.
I managed to get into the account because my other browser was still logged into my account, but I have found that things you change on the control panel do not take effect.
For example, when using the mass moderating page for comments, if you select the approve radio button and then click the Moderate button, it simply refreshes the page, without effecting the action.
I am now gonna check out that tool linked to above and see what it can do for me.