For whatever reason, in 3.1.3 (but not 3.1.2.sp1) columns in dataTable's have their CSS width set to "100px" by default. That causes the contents of the columns to wrap at 100px even if the actual column shows as much wider. The workaround is to put the width="auto" attribute on every rich:column.
To see the problem yourself:
This text will wrap. This text will wrap.
This text won't wrap. This text won't wrap. This text won't wrap.