[c-nsp] QoS sometimes drives me nuts

[Security Team]

I have really enjoyed learning about QoS, it's challenging.  But I ran
across something so simple today that doesn't work that I'm questioning
whether I have learned anything at all....

All I wanted to do on a 6500 with Sup2's is mark all incoming traffic into
my gig1/1 from a certain source address x.x.x.x to DSCP set to EF (46), like
this:

acc 101 permit udp x.x.x.x 0.0.0.255 any
acc 101 permit tcp x.x.x.x 0.0.0.255 any

class-map match-any IncomingVoiceTraffic
  match access-group 101

policy-map MarkIncomingVOIPTraffic
  class IncomingVoiceTraffic
    set ip dscp ef

interface GigabitEthernet1/1
 ip address blah blah
 service-policy input MarkIncomingVOIPTraffic

When I look with Wireshark the RTP packets for a voip session aren't getting
tagged inbound. Going back out gig1/1 is fine because the voip server is
marking the traffic properly. I'm just having trouble inbound.

Any gurus still awake?

Thanks,
CJ