Welcome to FlyerTalk water guy. A few possible ideas come to mind.
[*]I'm not certain, but the username and password may be case sensitive. If so, it is necessary to use caps and lower case exactly as you first signed up for FlyerTalk. [*]I also believe your browser needs to be set to accept cookies. (I'm not positive though). [*]If you did not provide a valid e-mail address during your sign-up process, your account may not validate. [*]You may wish to try the "lost password" link on any of the pages that require you to sign in or identify yourself. (The response from FlyerTalk requires a valid e-mail address).

I am perplexed about one thing, though! How were you able to post this message if you are not able to sign in?

Once again, welcome to FlyerTalk!