One of our users who uses AD for authentication was unable to login with the "£" symbol in their password. TIC was sending something else to the AD server, that was not the actual password, which caused their account to become locked out in Windows. (Perhaps it was sending the HTML-encoded variant "£" or "£") rather than the pound symbol. Changing the user's password to not have the "£" symbol resolved the issue.
Other special characters may also have this issue, but we haven't tested or encountered that scenario yet. Just putting this out there, in case other users have a similar problem.