Version:            (using KDE KDE 3.5.4)
Installed from:    Compiled From Sources
Compiler:          gcc (GCC) 4.1.2 20060901 (prerelease) (Debian 4.1.1-13) 
OS:                Linux

To reproduce it, set authentication method to something not supported. I set authentication method of my Gmail POP account to GSSAPI and dialog with following text appears while checking new mail:

"Authorization failed, An error occured during authentication: SASL(-1): generic failure: GSSAPI Error: Miscellaneous failure (No credentials cache found) authentication not supported"

Relevant code in the kio/kio/global.cpp file is:

case  KIO::ERR_COULD_NOT_AUTHENTICATE:
  result = i18n( "Authorization failed, %1 authentication not supported" ).arg( errorText );
  break;

It's obvious that %1 should contain only the name of authentication method, but really contains error message from server.