Hello Mike,
not sure if you have already done this, but before enabling Frame Relay fragmentation, you must first associate a Frame Relay map class with a specific data-link connection identifier (DLCI), and then enter map-class configuration mode and enable or disable fragmentation for that map class. In addition, you must enable Frame Relay traffic shaping on the interface in order for fragmentation to work.
Here is a config example from CCO (configure the DLCI part first):
interface Serial3/3
encapsulation frame-relay
frame-relay traffic-shaping
frame-relay interface-dlci 20
class data
frame-relay intf-type dce
!
map-class frame-relay data
frame-relay fragment 80
frame-relay cir 64000
frame-relay bc 640
Regards,
Georg