Characters not Displayed

Prior to my migrating from RHEL 5.5 to 6.0, when I used characters 
U+223b, U+227b, U+227f, U+2280 in formulae coded within OpenOffice 
Math (the formula editor) of OO 3.2.1, the document displayed these 
when viewed in OpenOffice, and an exported PDF displayed these when 
viewed with Acrobat readers.

Now, when the very same version of OpenOffice is used in RHEL 6.0, the 
character becomes invisible both in .ODTs and in .PDFs.

My suspicion is that the system UI used to make substitutions from 
another font file when a character were not in a specified font file, 
but is now not doing this.  Can someone either disabuse me of this 
suspicion, or tell me how to re-establish the substitutions?