If you need to enter character with accent in user name or password slim does not recognize them so you cannot login
Reproduced, and found an upstream bug too without comments however. Mike
You filled the bug http://bugs.debian.org/532060 in Debian BTS against the package slim. I'm closing it as fixed in *unstable*, but it will remain open for older distributions. For more information about this package's removal, read http://bugs.debian.org/538921. That bug might give the reasons why this package was removed and suggestions of possible replacements. Don't hesitate to reply to this mail if you have any question. Thank you for your contribution to Debian.
Actually it seems it only accepts English characters. Non-English ones like "ç" it doesn't recognize.