As Katie said, is there an ACL on the data already? That can certainly cause your display to give the appearance that nothing changed, when in fact the chmod was either ignored or the change you requested was merged in as an ACE into the ACL.
Look at it with ls -le /path , or if you have an ACL, and do an ls -l or ls -ld look for a plus sign to indicate that a REAL ACL exists and that the POSIX bits represented are synthetically generated based upon the ACL.
Advisory Solution Architect
Offer and Enablement Team
EMC²| Emerging Technologies Division