I think it might be the client version that's causing the problem. 4.1.1.0 introduced a fix for Bug 592 [0], but, in doing so, broke other things related to Kerberos, as reported in Bug 1258 [1] and (hopefully) fixed in 4.1.2.0.
Yes, updating to 4.1.2.1 through the PPA fixed it. Working perfectly with Kerberos now.
Thank you so much for the aid, Stefan.
Regards, Rubens