The method org.apache.poi.ss.usermodel.Sheet.autoSizeColumn(int i) works using the 32Bit swt libary (and 32Bit JVM) but it sets the columns unvisible using a 64Bit swt libary (and 64Bit JVM). I am using Java 1.7.21.
Sounds like either you don't have the fonts available to your 64 bit java install, or you have installed a broken JVM. Neither of those two cases would seem to be a POI bug, sorry...