[nsp] What does " Invalid weight assignment; default class weight < 1 " error using MQC?

[Joe Lin]

Dear List,
 
I am trying to configure dscp-based WRED using the below QoS policy on a
cisco 7505 running rsp-pv-mz.123-1a.bin and applying it to a serial port

 
policy-map test518
  class test518
    bandwidth 64
    queue-limit 200
    random-detect dscp-based
    random-detect dscp 0 100 200 5
    random-detect dscp 14 100 200 5
  class class-default
    queue-limit 20
    random-detect dscp-based
    random-detect dscp 0 3000 32000 40
 
When I apply this policy on a serial interface (4 port T1 PA) on a VIP2
Board
 
I get this error
 
Invalid weight assignment; default class weight < 1
 
Searching thru goggle and cisco didn't turn up with much :-(
 
Can anyone hand a clue?
 
Joe