The Ukrainian langpack is corrupt or uses non-standard UTF-8 characters. This is apparent by opening ukr.xml in a UTF-8 text editor or by selecting Ukrainian in izpack's own installer. Our bug report is at http://trac.i2p2.de/ticket/550
We verified this in izpack 4.3.0, 4.3.3, 4.3.4, and 5.0.0-beta8. "rndnick" from our project has done a new translation from scratch using the eng.xml from 4.3.0 as a base.
Attached to this ticket is his translation which can also be found in our bugtracker at http://trac.i2p2.de/raw-attachment/ticket/550/ukrnew-2.xml