I recently reset a password for a user, and the user is not able to login with this new password.
I tried it myself even, and even reset the password by pasting the same string in the reset fields as I did the login field.
I'm not getting complaints from any users about not being able to login, so hopefully this is just something to do with the password reset problem, and not a case where people after being frustrated and not contacting us about the issue.
By default, the new pw requirements for 1.9.3 are somewhat strict - try resetting to an 8 character password with at least 1 number and 1 non-alpha character.
You can also change the pw requirements via your web.config - several posts available on that subject here if you need it.