The username and password should be the same for both TWC and webcomic.net, in fact I just made the TWC link go to the reset password form here at webcomic.net temporarily.
If you have a different account you use to manage your TWC comic, please either use the reset form here on webcomic.net, or let me know the name of your account (that you use to log into twc) and I'll reset it myself and e-mail you the password to the e-mail address we have on file.
Thanks
Richard M.
Grimfang"Whisper"Xaeraes