Spaces at the beginning or ending of a password are trimmed off in the web but not in the client
The DLL is trimming any leading or trailing spaces from the password field within the web, whereas the client just runs the password as it's entered with the spaces. For example, if my password is "ABC" when logging in the client "ABC " fails, whereas it works in the web pages because the space is being removed.
Note: A space can exist within the password itself, e.g., "P@ss W0rd", as long as it's an accepted requirement in the Customization Manager. The spaces within the password will not be trimmed by the DLL.