At LinkedIn’s login page I requested a password reset. I immediately received a secure URL to a password change page where I created a new password. Subsequently I could not sign in using this new password. After trying every e-mail address I have thinking I had screwed up, no dice. I actually found my original password. With theory in mind, I requested a password reset. I then changed my password to my old password. Voila, I was able to login. I suppose LinkedIn is not refreshing their authentication server when the user changes their password.
UPDATE JULY 24, 2009 I found in the following blog the reason for the login failure: The password must be between 6 and 16 characters. I used more characters and the page said it was accepted. However LinkedIn truncated the password to the first 16 digits. So if you created a password longer than 16 digits, try logging in with the first 16 and you should be good to go. Lastly, I had no problem using symbols, upper and lowercase letters, and numbers in my password.
Credited article:

This limitation of 16 chars and – what is worse – silent truncation of stored password is still true in June 2010.
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